Data Sufficiency

BTGModeratorVI wrote: ↑

Fri Jul 03, 2020 7:16 am

What is the hundredths digit of the decimal z?

(1) The tenths digit is 100z is 2
(2) The units digit of 1,000z is 2

Answer: E
Source: GMAT prep

Target question: What is the hundredths digit of the decimal z?

Statement 1: The tenths digit of 100z is 2
Notice what happens when we take a decimal like 0.123456 and multiply it by 100.
We get 12.345 (the tenths digit is 3)
In the original decimal, the 3 was in the thousandths place.
So, statement 1 tells us that the THOUSANDTHS digit of z is 2
Since we cannot answer the target question with certainty, statement 1 is NOT SUFFICIENT

Statement 2: The unit digit of 1000z is 2
Notice what happens when we take a decimal like 0.123456 and multiply it by 1000.
We get 123.45 (the units digit is 3)
In the original decimal, the 3 was in the thousandths place.
So, statement 2 tells us that the THOUSANDTHS digit of z is 2
Since we cannot answer the target question with certainty, statement 2 is NOT SUFFICIENT

NOTE: Since statements 1 and 2 BOTH tell us the same thing (i.e., the THOUSANDTHS digit of z is 2), the combined statements are NOT SUFFICIENT

Answer: E

Cheers,
Brent