tanmay9 wrote:If x is the decimal 8.1d5, with d as an unknown digit, and x rounded to the nearest
tenth is equal to 8.1, which digits could not be the value of d?

according to me 4 should also be one of the digit values that cant be "d" but somehow manhattan says its till 5.

Pl help me understand.

8.105 rounded to the nearest tenth is 8.1
8.115 rounded to the nearest tenth is 8.1
8.125 rounded to the nearest tenth is 8.1
8.135 rounded to the nearest tenth is 8.1
8.145 rounded to the nearest tenth is 8.1

8.155 rounded to the nearest tenth is 8.2
8.165 rounded to the nearest tenth is 8.2
8.175 rounded to the nearest tenth is 8.2
etc

Are you sure that the MGMAT book says that 8.155 rounded to the nearest tenth is 8.1??


Cheers,
Brent

Hi tanmay9,

If we're rounding the number 8.1d5 to the nearest tenth and ending up with 8.1, then here's what we know about the digit d:

It COULD be 0, 1, 2, 3, or 4 because these numbers would round DOWN to the nearest tenth, giving us 8.1

It CANNOT be 5, 6, 7, 8, 9 because these numbers would round UP to the nearest tenth, giving us 8.2, which is NOT a match for what we're told.

In this question, it's worth noting that since we're rounding to the nearest tenth, the "5" in the thousanths place has NO EFFECT on the rounding.

The question asks for which digits COULD NOT be the value of d, so the answer is 5, 6, 7, 8, 9

GMAT assassins aren't born, they're made,
Rich

If you're rounding a number to the nearest tenth, then look at ONLY the hundredths digit. If it's 5 or greater, round up. If it's 4 or less, round down.

If you're rounding a number to the nearest hundredth, then look at ONLY the thousandths digit. If it's 5 or greater, round up. If it's 4 or less, round down.

If you're rounding a number to the nearest thousandth, then look at ONLY the ten-thousandths digit. If it's 5 or greater, round up. If it's 4 or less, round down.

etc

Cheers,
Brent