Fractions | IT

Question 25

Puzzle!

  1. Can you find three different fractional units that add up to 1?

    It turns out there is only one solution to this problem (up to changing the order of the 3 fractions)! Can you find it? Try to find it before reading further.

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Solution

We find three different fractions that add to one.

Step 1 — Find the first fraction

Let us call the three whole numbers aa, bb, and cc. The fractional units are 1/a1/a, 1/b1/b, and 1/c1/c. They must add up to 1. 1/a+1/b+1/c=11/a + 1/b + 1/c = 1 The numbers a,b,ca, b, c must be different. They must be whole numbers. If any number is 1, like a=1a=1. Then 1/1+1/b+1/c=11/1 + 1/b + 1/c = 1. This means 1+1/b+1/c=11 + 1/b + 1/c = 1. So 1/b+1/c1/b + 1/c must be 0. This is not possible for positive numbers. So a,b,ca, b, c must all be bigger than 1. Let us arrange them from smallest to largest. So a<b<ca < b < c. This means 1/a1/a is the biggest fraction. Let us try the smallest possible value for aa. The smallest whole number bigger than 1 is 2. So let us try a=2a = 2. We put 1/21/2 into the sum. 1/2+1/b+1/c=11/2 + 1/b + 1/c = 1 Now we find what 1/b+1/c1/b + 1/c is. We take away 1/21/2 from 1. 1/b+1/c=11/21/b + 1/c = 1 - 1/2 1/b+1/c=1/21/b + 1/c = 1/2

Diagram 1

Step 2 — Find the second fraction

Now we find two different fractions. They must add up to 1/21/2. We know bb must be bigger than aa. So bb must be bigger than 2. Also, bb must be smaller than cc. So 1/b1/b must be bigger than 1/c1/c. This means 1/b1/b is more than half of 1/21/2. Half of 1/21/2 is 1/41/4. So 1/b1/b must be bigger than 1/41/4. This means bb must be smaller than 4. So bb must be bigger than 2. It must be smaller than 4. The only whole number that fits is 3. So let us try b=3b = 3. We put 1/31/3 into the sum. 1/3+1/c=1/21/3 + 1/c = 1/2 Now we find what 1/c1/c is. We take away 1/31/3 from 1/21/2. 1/c=1/21/31/c = 1/2 - 1/3 To subtract, we find a common bottom number. The common bottom number is 6. We change 1/21/2 to 3/63/6. We change 1/31/3 to 2/62/6. 1/c=3/62/61/c = 3/6 - 2/6 1/c=1/61/c = 1/6

Diagram 2

Step 3 — Find the third fraction

From the last step, we found 1/c=1/61/c = 1/6. This means cc must be 6. Let us check if this works. We need cc to be different from a,ba, b. Our numbers are 2, 3, and 6. They are all different whole numbers. Yes! We also need cc to be bigger than bb. Is 6 bigger than 3? Yes! So the units are 1/21/2, 1/31/3, 1/61/6. Let us add them up to check. 1/2+1/3+1/61/2 + 1/3 + 1/6 We find a common bottom number. The common bottom number is 6. We change 1/21/2 to 3/63/6. We change 1/31/3 to 2/62/6. 1/61/6 stays as 1/61/6. =3/6+2/6+1/6= 3/6 + 2/6 + 1/6 =(3+2+1)/6= (3+2+1)/6 =6/6= 6/6

1\boxed{1} The sum is 1. This is the only solution. We found that aa must be 2. Then bb must be 3. Then cc must be 6. No other whole numbers work.

Answer

(i) The units are 1/21/2, 1/31/3, 1/61/6.

More questions in IT

Q1

Arrange these fraction words in order of size from the smallest to the biggest in the empty box below:

One and a half, three quarters, one and a quarter, half, quarter, two and a half.

Q2

By dividing the whole chikki into 6 equal parts in different ways, we get 1/6 chikki pieces of different shapes. Are they of the same size?

Q3

Do it once more! Fill in the blank boxes.

Q4

Now, can you find the lengths of the various blue lines shown below? Fill in the boxes as well.

  1. Here, the fractional unit is dividing a length of 1 unit into three equal parts. Write the fraction that gives the length of the blue line in the box or in your notebook.
Q5

Here, a unit is divided into 5 equal parts. Write the fraction that gives the length of the blue lines in the respective boxes or in your notebook.

Q6

Now, a unit is divided into 8 equal parts. Write the appropriate fractions in your notebook.

Q7

Write down all the fractions you marked on the number line earlier.

Now, let us classify these in two groups:

Q8

Did you notice something common between the fractions that are greater than 1?

Q9

What do you observe?

  • Are the lengths 12\frac{1}{2} and 24\frac{2}{4} equal?
  • Are the lengths 24\frac{2}{4} and 48\frac{4}{8} equal?
Q10

Now, check whether 13\frac{1}{3} and 26\frac{2}{6} are equivalent fractions or not, using paper strips.

Q11

Answer the following questions after looking at the fraction wall:

Are the lengths 12\frac{1}{2} and 36\frac{3}{6} equal?

Q12

Answer the following questions after looking at the fraction wall:

Are 23\frac{2}{3} and 46\frac{4}{6} equivalent fractions? Why?

Q13

Answer the following questions after looking at the fraction wall:

How many pieces of length 16\frac{1}{6} will make a length of 12\frac{1}{2}?

Q14

Answer the following questions after looking at the fraction wall:

How many pieces of length 16\frac{1}{6} will make a length of 13\frac{1}{3}?

Q15

Context: Anil was in a group where 2 cakes were divided equally among 5 children.

Q. Now, if there are 10 children in my group, how many cakes will I need so that they get same amount of cake as Anil?

Q16

Q. What if we put two such groups together? One group where 2 cakes are divided equally between 5 children, and another group again with 4 cakes and 10 children.

Q17

Find some more fractions equivalent to 12\frac{1}{2}. Write them in the boxes here:

Q18

Equally divide the rotis in the situations shown below and write down the share of each child. Are the shares in each of these cases the same? Why?

Q19

Suppose the number of children is kept the same, but the number of units that are being shared is increased? What can you say about each child's share now? Why? Discuss how your reasoning explains 15<25\frac{1}{5} < \frac{2}{5}, 37<47\frac{3}{7} < \frac{4}{7}, and 12<58\frac{1}{2} < \frac{5}{8}.

Q20

Now, decide in which of the two groups will each child get a larger share:

  1. Group 1: 3 glasses of sugarcane juice divided equally among 4 children. Group 2: 7 glasses of sugarcane juice divided equally among 10 children.
  2. Group 1: 4 glasses of sugarcane juice divided equally among 7 children. Group 2: 5 glasses of sugarcane juice divided equally among 7 children.

Which groups were easier to compare? Why?

Q21

Find equivalent fractions for the given pairs of fractions such that the fractional units are the same.

a. 72\frac{7}{2} and 35\frac{3}{5}

b. 83\frac{8}{3} and 56\frac{5}{6}

c. 34\frac{3}{4} and 35\frac{3}{5}

d. 67\frac{6}{7} and 85\frac{8}{5}

e. 94\frac{9}{4} and 52\frac{5}{2}

f. 110\frac{1}{10} and 29\frac{2}{9}

g. 83\frac{8}{3} and 114\frac{11}{4}

h. 136\frac{13}{6} and 19\frac{1}{9}

Q22

Context: Meena's father made some chikki. Meena ate 12\frac{1}{2} of it and her younger brother ate 14\frac{1}{4} of it.

Q. How much of the total chikki is remaining?

Q23

Try adding 47+67\frac{4}{7} + \frac{6}{7} using a number line. Do you get the same answer?

Q24

Try doing this same exercise using the number line.

Q25

Puzzle!

  1. Can you find three different fractional units that add up to 1?

    It turns out there is only one solution to this problem (up to changing the order of the 3 fractions)! Can you find it? Try to find it before reading further.

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