Sign in
Please select an account to continue using cracku.in
↓ →
Join Our JEE Preparation Group
Prep with like-minded aspirants; Get access to free daily tests and study material.
The smallest positive integer $$n$$ for which $$18900 \times n$$ is a perfect cube is
Given
$$18900\times n$$ is a perfect cube.
Β Step 1: Prime factorize 18900
$$18900=189\times100$$
$$=3^3\times7\times2^2\times5^2$$
Therefore,
$$18900=2^2\times3^3\times5^2\times7.$$
Β Step 2: Make the powers multiples of 3
For a number to be a perfect cube, the power of every prime factor must be a multiple of $$3$$.
We have $$18900=2^2\times3^3\times5^2\times7^1.$$
Therefore, we need to multiply by: $$2^1$$Β to make the power of $$2$$ equal to $$3$$,
$$5^1$$ to make the power of $$5$$ equal to $$3$$,
and $$7^2$$ to make the power of $$7$$ equal to $$3$$.
Hence, $$n=2\times5\times7^2.$$
$$=2\times5\times49.$$
$$=490.$$
Final answer $$\boxed{490}$$
Click on the Email βοΈ to Watch the Video Solution
Predict your JEE Main percentile, rank & performance in seconds
Educational materials for JEE preparation