Data Sufficiency

Hi, can someone teach me how to approach problem like this especially Q26( i see this question quite often but don't know how to deal with it/ is there any pattern to solve it)?


For Q29, i thought stmt I alone is sufficient, but why the answer is c?



Thanks a lot

Q 20: https://www.beatthegmat.com/gmat-prep-2- ... 17705.html

Q:29

The first digit to the right of decimal is tenths, 2nd hundreths, 3rd thousandths etc...

When u are asked to round to a certain place value then u look to the right of it . If that(the right of it) is 1-4 then the value in the place u need to round to stays the same. If that is 5-9 then u add 1 to the place u need to round to

Stmt I

When x is rounded to the nearest thousandths the result is .455

The decimal could have been .4549

Rounded to the thousandths place the decimal is .455

Or

The decimal could have been .4551


Rounded to the thousandths place the decimal is .455

INSUFF

Stmt II

The thousandths digit of x is 5

Decimal = .455 then rounded to the hundreths it is .46
Decimal = .425 then rounded to the hundreths it is .43

INSUFF

Together:

The decimal rounded to the nearest hundreths has to be .46

SUFF

Hope this helps!

Regards,
CR