is the hundredths digit of the decimal d greater than 5?
1) The tenths digit of 10d is 7.
2) The thousandths digit of d/10 is 7.





(1) Suppose 10d=***.7***, in which each star represents a digit, whether equal or unequal.
d=**.*7***. So the hundredths digit is 7. Sufficient.
(2) Similarly, this statement is also sufficient.
D

Note ----
the thousandths digit and the thousands digit are completely different digits, and are not to be confused with one another.
the thousands digit is 4 spots to the left of the decimal point: e.g., the '1' in 1000. the thousandths digit is 3 spots to the right of the decimal point: e.g., the '1' in 0.001.
in general, if a place value ends in '-ths', then that place value signifies a DECIMAL place; if it doesn't, then it signifies one of the INTEGER places (i.e., the ones to the left of the decimal point).
same distinction goes for the tens place (2 spots to the left of the decimal point) and the tenths place (one spot to the right of the decimal point).
watch the distinction, and try not to confuse them - each spot has a unique name!