nearest thousandth

vk_vinayak wrote:If p = 5.18r7, what is the result when p is subtracted from p rounded to the nearest thousandth?

Can we find the answer to this problem without the help of options?

Answer is 3 * 10^-4 = 0.0003

Explanation = 5.18(r+1) when rounded to nearest thousand
original number = 5.18r7

so when 5.18(r+1) - 5.18r7 = ((r + 1) * 10 ^ -3) - (r * 10 ^ -3 + 7 * 10 ^ -4)

=> (r * 10 ^ -3 + 1 * 10 ^ -3 - r * 10 ^ -3 - 7 * 10 ^ -4)

=> (10 * 10 ^ -4 - 7 * 10 ^ -4)
=> 3 * 10 ^ -4 = 0.0003

That is correct, but the calculation is lengthy.

I guess we are better off using substitution method.