Find The cube roots of the numbers 3048625, 20346417, 210644875, 57066625 using the fact that
(i) 3048625 = 3375 × 729
(ii) 20346417 = 9261 × 2197
(iii) 210644875 = 42875 × 4913
(iv) 57066625 = 166375 × 343
(i)
To find the cube root, we use the following property:
$\sqrt[3]{a b}=\sqrt[3]{a} \times \sqrt[3]{b}$ for two integers $a$ and $b$
now
$\sqrt[3]{3048625}$
$=\sqrt[3]{3375} \times 729$
$=\sqrt[3]{3375} \times \sqrt[3]{729}$ (By the above property)
$=\sqrt[3]{3 \times 3 \times 3 \times 5 \times 5 \times 5} \times \sqrt[3]{9 \times 9 \times 9} \quad$ (By prime factorisation)
$=\sqrt[3]{\{3 \times 3 \times 3\} \times\{5 \times 5 \times 5\}} \times \sqrt[3]{\{9 \times 9 \times 9\}}$
$=3 \times 5 \times 9$
$=3 \times 5 \times 9$
$=135$
Thus, the answer is 135.
(ii)
To find the cube root, we use the following property:
$\sqrt[3]{a b}=\sqrt[3]{a} \times \sqrt[3]{b}$ for two integers $a$ and $b$
Now,
$\sqrt[3]{20346417}$
$=\sqrt[3]{9261} \times 2197$
$=\sqrt[3]{9261} \times \sqrt[3]{2197}$ (By the above property)
$=\sqrt[3]{3 \times 3 \times 3 \times 7 \times 7 \times 7} \times \sqrt[3]{13 \times 13 \times 13}$ (By prime factorisation)
$=\sqrt[3]{\{3 \times 3 \times 3\} \times\{7 \times 7 \times 7\}} \times \sqrt[3]{\{13 \times 13 \times 13\}}$
$=3 \times 7 \times 13$
$=273$
Thus, the answer is 273.
(iii)
To find the cube root, we use the following property:
$\sqrt[3]{a b}=\sqrt[3]{a} \times \sqrt[3]{b}$ for two integers $a$ and $b$
Now
$\sqrt[3]{210644875}$
$=\sqrt[3]{42875} \times 4913$
$=\sqrt[3]{42875} \times \sqrt[3]{4913}$ (By the above property)
$=\sqrt[3]{5 \times 5 \times 5 \times 7 \times 7 \times 7} \times \sqrt[3]{17 \times 17 \times 17}$ (By prime factorisation)
$=\sqrt[3]{\{5 \times 5 \times 5\} \times\{7 \times 7 \times 7\}} \times \sqrt[3]{\{17 \times 17 \times 17\}}$
$=5 \times 7 \times 17$
$=595$
Thus, the answer is 595.
(iv)
To find the cube root, we use the following property:
$\sqrt[3]{a b}=\sqrt[3]{a} \times \sqrt[3]{b}$ for two integers $a$ and $b$
now
$\sqrt[3]{57066625}$
$=\sqrt[3]{166375} \times 343$
$=\sqrt[3]{166375} \times \sqrt[3]{343}$ (By the above property)
$=\sqrt[3]{5 \times 5 \times 5 \times 11 \times 11 \times 11} \times \sqrt[3]{7 \times 7 \times 7} \quad$ (By prime factorisation)
$=\sqrt[3]{\{5 \times 5 \times 5\} \times\{11 \times 11 \times 11\} \times \sqrt[3]{\{7 \times 7 \times 7\}}}$
$=5 \times 11 \times 7$
$=385$
Thus, the answer is 385.