Could someone please provide an explanation as to how one got the answer, that is D. How did the 7 move from the tenths place to the hundredths place? Did I miss something?
you shouldn't think of it as though the 7 has moved; you should think of it as though the decimal point
has moved. in fact, this is precisely what has happened, as both statements involving multiplication by powers of 10 (which serves to move the decimal point while leaving the digits themselves unaffected).
here's the deal:
you are interested in the hundredths place of the original number 'd'. to wit, let's write 'd' as a succession of decimal places:
d = XXXXXX.XXXX...
in this version, the orange digit is the one in which you're interested.
statement (1) concerns the number 10d, not d. when you multiply by 10, the decimal point is shifted to the right by one spot, so that the ones digit becomes the new tens digit and so on. so, with 'd' represented as above, you can write
10d = XXXXXXX.XXX...
according to statement (1), then, the orange digit is 7, so statement (1) is sufficient.
statement (2) concerns the number d/10, not d. when you divide by 10, the decimal point is shifted to the left by one spot, so that the tens digit becomes the new ones digit and so on. so, with 'd' represented as above, you can write
d/10 = XXXXX.XXXXX...
according to statement (2), then, the orange digit is 7, so statement (2) is sufficient.