fdp problem

[me]

if k is a positive three-digit integer, what is the hundreds digit of k?

1. the hundreds digit of k + 150 is 4.

2. the tens digit of k + 25 is 7.

why doesn't A work here?

got this from mgmat question bank. thanks for your help.

[shaji]

k could be 280 or 320 and notice the 2 different hundred's digitof k; so statement 1 is INSUFFICIENT.

if k is a positive three-digit integer, what is the hundreds digit of k?

1. the hundreds digit of k + 150 is 4.

2. the tens digit of k + 25 is 7.

why doesn't A work here?

got this from mgmat question bank. thanks for your help.

[RonPurewal]

In general, with problems like this one, just consider the EXTREMES of any possible range they throw at you.

If the hundreds digit of (k + 150) is 4, then take that to mean that
400 <= k + 150 <= 499
or
250 <= k <= 349.

Therefore, the hundreds digit of k can be either 2 or 3, so this statement is insufficient.

Note that you don't have to set up the inequalities to solve the problem: you can just notice that the biggest possible value for (k + 150) is 499, and that the smallest possible value for that expression is 400. In any case, it's much better to consider extremes for a problem like this than to pick numbers like the ones in the previous post (which are, for all intents and purposes, random choices - not the best way to get started on a problem with a definite range of numbers).

[PudGe]

Ron,
i found your approach pretty useful here.

for Stmt 2) do we adopt the same approach ?
i.e 170 <= k+25 <= 970
so since there are numerous possibilities for the hundereds digit -This is also insufficient.

combining (1) +(2)
this still doesnt give us a definite value for hundereds digit of k ( i am not sure how to come down to this - can you pls add your 2 cents .

Thanks.

[tim]

mostly correct. the problem is that k+25 can't be just anything from 170 to 970; it can only be certain numbers: 170, 270, 370, ..., 970

[garima_aries01]

Is the answer to this question E?

[tim]

from statement 1, k could be anything from 250 to 349. from statement 2, k could be any number whose last two digits are between 45 and 54 inclusive. so k could, for instance, be 251 or 348, and therefore there are two possibilities for the hundreds digit. so yes, the answer is E..

[supratim7]

If k is a positive three-digit integer, what is the hundreds digit of k?

1. the hundreds digit of k + 150 is 4.
2. the tens digit of k + 25 is 7.

1. the hundreds digit of k + 150 is 4.
MIN value for k + 150 = 400 & MAX value for k + 150 = 499
So, MIN value for k = 250 & MAX value for k = 349

INSUFFICIENT

2. the tens digit of k + 25 is 7.
MIN value for k+25's first 2 digits = 70 & MAX value for k+25's first 2 digits = 79
So, MIN value for k's first 2 digits = 45 & MAX value for k's first 2 digits = 54

INSUFFICIENT

(1) + (2)
MIN value for k = 250 & MAX value for k = 349
MIN value for k's first 2 digits = 45 & MAX value for k's first 2 digits = 54
So, Possible values of k = 250 to 254 & 345 to 349

INSUFFICIENT (E)

[tim]

Pretty much what I said in September. :)