Large Numbers Around Us | FIO

Question 22

You are given some number cards; 4000, 13000, 3000, 70000, 150000, 20, 5. Using the cards get as close as you can to the numbers below using any operation you want. Each card can be used only once for making a particular number.

(a) 1,10,000: Closest I could make is 4000 × (20 + 5) + 13000 = 1,13,000

(b) 2,00,000:

(c) 5,80,000:

(d) 12,45,000:

(e) 20,90,800:

Check your answer with HomiSolve it yourself, then let Homi check your steps and spot mistakes.
Solution

We will use the given number cards and mathematical operations to get as close as possible to each target number. Each card can be used only once for each target.

Step 1 — Target 2,00,000

We want to reach 2,00,000. Let us try to combine the largest numbers first. We can add 1,50,000 and 70,000.

1,50,000+70,0001,50,000 + 70,000

=2,20,000= 2,20,000

This is 20,000 more than our target. We need to subtract 20,000. Let us see if we can make 20,000 from the remaining cards. The remaining cards are 4000, 13000, 3000, 20, 5. We can multiply 4000 by 5.

4000×54000 \times 5

=20,000= 20,000

Now, let us subtract this from 2,20,000.

2,20,00020,0002,20,000 - 20,000

=2,00,000= 2,00,000

This is exactly the target number. The cards used are 1,50,000, 70,000, 4000, and 5. Each card is used once.

1,50,000+70,000(4000×5)=2,00,000\boxed{1,50,000 + 70,000 - (4000 \times 5) = \mathbf{2,00,000}}

Diagram 1

Step 2 — Target 5,80,000

We want to reach 5,80,000. This is a large number. Let us try multiplying the largest cards by 5 or 20. If we multiply 70,000 by 5, we get 3,50,000.

70,000×570,000 \times 5

=3,50,000= 3,50,000

We need 5,80,000 - 3,50,000 = 2,30,000 more. The cards used are 70,000 and 5. The remaining cards are 4000, 13000, 3000, 150000, 20. We have 1,50,000. We need 2,30,000 - 1,50,000 = 80,000 more. Let us try to make 80,000 from the remaining cards: 4000, 13000, 3000, 20. We can multiply 4000 by 20.

4000×204000 \times 20

=80,000= 80,000

Now, let us combine these parts.

(70,000×5)+1,50,000+(4000×20)(70,000 \times 5) + 1,50,000 + (4000 \times 20)

=3,50,000+1,50,000+80,000= 3,50,000 + 1,50,000 + 80,000

=5,00,000+80,000= 5,00,000 + 80,000

=5,80,000= 5,80,000

This is exactly the target number. The cards used are 70,000, 5, 1,50,000, 4000, and 20. Each card is used once.

(70,000×5)+1,50,000+(4000×20)=5,80,000\boxed{(70,000 \times 5) + 1,50,000 + (4000 \times 20) = \mathbf{5,80,000}}

Diagram 2

Step 3 — Target 12,45,000

We want to reach 12,45,000. This is a very large number. Let us try multiplying a large card by 20. If we multiply 70,000 by 20, we get 14,00,000.

70,000×2070,000 \times 20

=14,00,000= 14,00,000

This is more than our target. We need to subtract 14,00,000 - 12,45,000 = 1,55,000. The cards used are 70,000 and 20. The remaining cards are 4000, 13000, 3000, 150000, 5. We have 1,50,000. We need to subtract 1,55,000. If we subtract 1,50,000, we get 14,00,000 - 1,50,000 = 12,50,000.

(70,000×20)1,50,000(70,000 \times 20) - 1,50,000

=14,00,0001,50,000= 14,00,000 - 1,50,000

=12,50,000= 12,50,000

This number is 12,50,000. Our target is 12,45,000. The difference is 12,50,000 - 12,45,000 = 5000. The cards used are 70,000, 20, and 1,50,000. The remaining cards are 4000, 13000, 3000, 5. We cannot make 5000 to subtract. Let us try another way to get close. Consider multiplying a sum of large numbers by 5. Let us add 1,50,000 and 70,000.

1,50,000+70,0001,50,000 + 70,000

=2,20,000= 2,20,000

Now, multiply this sum by 5.

2,20,000×52,20,000 \times 5

=11,00,000= 11,00,000

We have 11,00,000. Our target is 12,45,000. We need 12,45,000 - 11,00,000 = 1,45,000 more. The cards used are 1,50,000, 70,000, and 5. The remaining cards are 4000, 13000, 3000, 20. Let us try to make 1,45,000 from these cards. Let us add 4000 and 3000.

4000+30004000 + 3000

=7000= 7000

Now, multiply this sum by 20.

7000×207000 \times 20

=1,40,000= 1,40,000

Now, let us combine these parts.

(1,50,000+70,000)×5+(4000+3000)×20(1,50,000 + 70,000) \times 5 + (4000 + 3000) \times 20

=2,20,000×5+7000×20= 2,20,000 \times 5 + 7000 \times 20

=11,00,000+1,40,000= 11,00,000 + 1,40,000

=12,40,000= 12,40,000

This number is 12,40,000. Our target is 12,45,000. The difference is 12,45,000 - 12,40,000 = 5000. The cards used are 1,50,000, 70,000, 5, 4000, 3000, and 20. The remaining card is 13000. We cannot make 5000 from 13000. Both 12,50,000 and 12,40,000 are 5000 away from 12,45,000. We can choose either one. Let us choose the one that uses more cards as it shows more operations.

(1,50,000+70,000)×5+(4000+3000)×20=12,40,000\boxed{(1,50,000 + 70,000) \times 5 + (4000 + 3000) \times 20 = \mathbf{12,40,000}}

Diagram 3

Step 4 — Target 20,90,800

We want to reach 20,90,800. This is a very large number. Let us try to combine large numbers and multiply by (20 + 5). Let us add 70,000 and 13,000.

70,000+13,00070,000 + 13,000

=83,000= 83,000

Let us add 20 and 5.

20+520 + 5

=25= 25

Now, multiply these two sums.

83,000×2583,000 \times 25

=20,75,000= 20,75,000

We have 20,75,000. Our target is 20,90,800. The difference is 20,90,800 - 20,75,000 = 15,800. The cards used are 70,000, 13,000, 20, and 5. The remaining cards are 4000, 3000, 150000. We need to add 15,800. Let us try to make a number close to 15,800 from the remaining cards. If we add 4000 and 3000, we get 7000.

4000+30004000 + 3000

=7000= 7000

Now, let us add this to 20,75,000.

More questions in FIO

Q1

According to the 2011 Census, the population of the town of Chintamani was about 75,000. How much less than one lakh is 75,000?

Q2

The estimated population of Chintamani in the year 2024 is 1,06,000. How much more than one lakh is 1,06,000?

Q3

By how much did the population of Chintamani increase from 2011 to 2024?

Q4

For each number given below, write expressions for at least two different ways to obtain the number through button clicks. Think like Chitti and be creative.

(a) 8300

(b) 40629

(c) 56354

(d) 66666

(e) 367813

Q5

For the numbers in the previous exercise, find out how to get each number by making the smallest number of button clicks and write the expression.

Q6

Do you see any connection between each number and the corresponding smallest number of button clicks?

Q7

If you notice, the expressions for the least button clicks also give the Indian place value notation of the numbers. Think about why this is so.

Q8

Read the following numbers in Indian place value notation and write their number names in both the Indian and American systems:

(a) 4050678

(b) 48121620

(c) 20022002

(d) 246813579

(e) 345000543

(f) 1020304050

Q9

Write the following numbers in Indian place value notation:

(a) One crore one lakh one thousand ten

(b) One billion one million one thousand one

(c) Ten crore twenty lakh thirty thousand forty

(d) Nine billion eighty million seven hundred thousand six hundred

Q10

Compare and write '<', '>' or '=':

(a) 30 thousand ______ 3 lakhs

(b) 500 lakhs ______ 5 million

(c) 800 thousand ______ 8 million

(d) 640 crore ______ 60 billion

Q11

Find quick ways to calculate these products:

(a) 2×1768×502 \times 1768 \times 50

(b) 72×12572 \times 125 [Hint: 125=10008125 = \frac{1000}{8}]

(c) 125×40×8×25125 \times 40 \times 8 \times 25

Q12

Calculate these products quickly.

(a) 25×12=25 \times 12 = _______

(b) 25×240=25 \times 240 = _______

(c) 250×120=250 \times 120 = _______

(d) 2500×12=2500 \times 12 = _______

(e) _______ ×\times _______ =120000000= 120000000

Q13

Using all digits from 0 – 9 exactly once (the first digit cannot be 0) to create a 10-digit number, write the —

(a) Largest multiple of 5

(b) Smallest even number

Q14

The number 10,30,285 in words is Ten lakhs thirty thousand two hundred eighty five, which has 42 letters. Give a 7-digit number name which has the maximum number of letters.

Q15

Write a 9-digit number where exchanging any two digits results in a bigger number. How many such numbers exist?

Q16

Strike out 10 digits from the number 12345123451234512345 so that the remaining number is as large as possible.

Q17

The words 'zero' and 'one' share letters 'e' and 'o'. The words 'one' and 'two' share a letter 'o', and the words 'two' and 'three' also share a letter 't'. How far do you have to count to find two consecutive numbers which do not share an English letter in common?

Q18

Suppose you write down all the numbers 1, 2, 3, 4, ..., 9, 10, 11, ... The tenth digit you write is '1' and the eleventh digit is '0', as part of the number 10.

(a) What would the 1000th digit be? At which number would it occur?

(b) What number would contain the millionth digit?

(c) When would you have written the digit '5' for the 5000th time?

Q19

A calculator has only '+10,000' and '+100' buttons. Write an expression describing the number of button clicks to be made for the following numbers:

(a) 20,800 (b) 92,100 (c) 1,20,500 (d) 65,30,000 (e) 70,25,700

Q20

How many lakhs make a billion?

Q21

You are given two sets of number cards numbered from 1-9. Place a number card in each box below to get the

(a) largest possible sum

(b) smallest possible difference of the two resulting numbers.

Q22

You are given some number cards; 4000, 13000, 3000, 70000, 150000, 20, 5. Using the cards get as close as you can to the numbers below using any operation you want. Each card can be used only once for making a particular number.

(a) 1,10,000: Closest I could make is 4000 × (20 + 5) + 13000 = 1,13,000

(b) 2,00,000:

(c) 5,80,000:

(d) 12,45,000:

(e) 20,90,800:

Q23

Find out how many coins should be stacked to match the height of the Statue of Unity. Assume each coin is 1 mm thick.

Q24

Grey-headed albatrosses have a roughly 7-feet wide wingspan. They are known to migrate across several oceans. Albatrosses can cover about 900 – 1000 km in a day. One of the longest single trips recorded is about 12,000 km. How many days would such a trip take to cross the Pacific Ocean approximately?

Q25

A bar-tailed godwit holds the record for the longest recorded non-stop flight. It travelled 13,560 km from Alaska to Australia without stopping. Its journey started on 13 October 2022 and continued for about 11 days. Find out the approximate distance it covered every day. Find out the approximate distance it covered every hour.

Q26

Bald eagles are known to fly as high as 4500 – 6000 m above the ground level. Mount Everest is about 8850 m high. Aeroplanes can fly as high as 10,000 – 12,800 m. How many times bigger are these heights compared to Somu’s building?

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