Rational Numbers | FIO

Question 10

Find the cube roots of 27000 and 10648.

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Solution

We will find the cube root of each number by breaking it down into its prime factors.

Step 1 — Prime Factorization of 27000

We divide 27000 by prime numbers until we reach 1. A prime number is a whole number greater than 1 with only two divisors: 1 and itself.

27000÷2=1350027000 \div 2 = 13500

13500÷2=675013500 \div 2 = 6750

6750÷2=33756750 \div 2 = 3375

3375÷3=11253375 \div 3 = 1125

1125÷3=3751125 \div 3 = 375

375÷3=125375 \div 3 = 125

125÷5=25125 \div 5 = 25

25÷5=525 \div 5 = 5

5÷5=15 \div 5 = 1

So, the prime factorization of 27000 is: 27000=2×2×2×3×3×3×5×5×527000 = 2 \times 2 \times 2 \times 3 \times 3 \times 3 \times 5 \times 5 \times 5

Step 2 — Finding the Cube Root of 27000

We group the prime factors into sets of three identical factors. The cube root is found by taking one factor from each group.

270003=(2×2×2)×(3×3×3)×(5×5×5)3\sqrt[3]{27000} = \sqrt[3]{(2 \times 2 \times 2) \times (3 \times 3 \times 3) \times (5 \times 5 \times 5)}

=2×3×5= 2 \times 3 \times 5

=6×5= 6 \times 5

30\boxed{30}

Step 3 — Prime Factorization of 10648

We divide 10648 by prime numbers until we reach 1.

10648÷2=532410648 \div 2 = 5324

5324÷2=26625324 \div 2 = 2662

2662÷2=13312662 \div 2 = 1331

We check for divisibility by other prime numbers. We find that 1331 is divisible by 11.

1331÷11=1211331 \div 11 = 121

121÷11=11121 \div 11 = 11

11÷11=111 \div 11 = 1

So, the prime factorization of 10648 is: 10648=2×2×2×11×11×1110648 = 2 \times 2 \times 2 \times 11 \times 11 \times 11

Step 4 — Finding the Cube Root of 10648

We group the prime factors into sets of three identical factors. The cube root is found by taking one factor from each group.

106483=(2×2×2)×(11×11×11)3\sqrt[3]{10648} = \sqrt[3]{(2 \times 2 \times 2) \times (11 \times 11 \times 11)}

=2×11= 2 \times 11

22\boxed{22}

Answer

(i) The cube root of 27000 is 30. (ii) The cube root of 10648 is 22.

More questions in FIO

Q1

Which of the following numbers are not perfect squares?

(i) 2032 (ii) 2048 (iii) 1027 (iv) 1089

Q2

Which one among 64264^2, 1082108^2, 2922292^2, 36236^2 has last digit 4?

Q3

Given 1252=15625125^2 = 15625, what is the value of 1262126^2?

(i) 15625 + 126

(ii) 15625+26215625 + 26^2

(iii) 15625 + 253

(iv) 15625 + 251

(v) 15625+51215625 + 51^2

Q4

Find the length of the side of a square whose area is 441 m2441\text{ m}^2.

Q5

Find the smallest square number that is divisible by each of the following numbers: 4, 9, and 10.

Q6

Find the smallest number by which 9408 must be multiplied so that the product is a perfect square. Find the square root of the product.

Q7

How many numbers lie between the squares of the following numbers?

(i) 16 and 17 (ii) 99 and 100

Q8

In the following pattern, fill in the missing numbers:

12+22+22=321^2 + 2^2 + 2^2 = 3^2 22+32+62=722^2 + 3^2 + 6^2 = 7^2 32+42+122=1323^2 + 4^2 + 12^2 = 13^2

(a) 42+52+202=()24^2 + 5^2 + 20^2 = (\underline{\quad})^2

(b) 92+102+()2=()29^2 + 10^2 + (\underline{\quad})^2 = (\underline{\quad})^2

Q9

How many tiny squares are there in the following picture? Write the prime factorisation of the number of tiny squares.

Q10

Find the cube roots of 27000 and 10648.

Q11

What number will you multiply by 1323 to make it a cube number?

Q12

State true or false. Explain your reasoning.

(i) The cube of any odd number is even.

(ii) There is no perfect cube that ends with 8.

(iii) The cube of a 2-digit number may be a 3-digit number.

(iv) The cube of a 2-digit number may have seven or more digits.

(v) Cube numbers have an odd number of factors.

Q13

You are told that 1331 is a perfect cube. Can you guess without factorisation what its cube root is? Similarly, guess the cube roots of 4913, 12167, and 32768.

Q14

Which of the following is the greatest? Explain your reasoning.

(i) 67366367^3 - 66^3

(ii) 43342343^3 - 42^3

(iii) 67266267^2 - 66^2

(iv) 43242243^2 - 42^2

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