[Math Revolution GMAT math practice question]

\([x]\) is the greatest integer less than or equal \(x\), what is the value of \([√30]+[√40]+[√50]?\)

\(A. 12\)
\(B. 15\)
\(C. 16\)
\(D. 18\)
\(E. 20\)
_________________

GIVEN: [x] is the greatest integer less than or equal x
For example, [3.2] = 3, since 3 is the greatest integer that is less than (or equal) to 3.2
Likewise, [8.7] = 8, since 8 is the greatest integer that is less than (or equal to) 8.7

Now onto the question....
√25 = 5
√36 = 6
√49= 7
√64 = 8

Since √30 is BETWEEN √25 (aka 5) and √36 (aka 6), we know that √30 = 5.something
So, [√30] = 5

Since √40 is BETWEEN √36 (aka 6) and √49 (aka 6), we know that √40 = 6.something
So, [√40] = 6

Since √50 is BETWEEN √49 (aka 7) and √64 (aka 8), we know that √50 = 7.something
So, [√50] = 7

So, [√30]+[√40]+[√50] = 5 + 6 + 7 = 18

Answer: D

Cheers,
Brent
_________________