Problem Solving

70 students are required to paint a picture. 52 use green color and some children use red, 38 students use both the colors. How many students use red color? A) 24 B) 42 C) 56 D)70

hi friends tell me wat this type probs s called. also tell me any formula to work out these type of probs.

This problem is based on sets.

The formula for 2 elements (A and B) of sets,

P(AuB)=P(A)+P(B)-P(AnB)

70=52+P(R)-38

P(R)=56

Hi Bubbly Rathi,

These are set theory questions. Please check your other question in which the trainer - learner - dancer has been discussed. The relationship between union, intersection and the individual sets has been provided there also.

Here goes ...

n(A union B) = n (A) + n (B) - n(A intersection B)

Note that, if there are 3 items,

n (A union B union C) =

n(A) + n(B) + n(C)
-n(A intersection B) - n(B intersection C) - n(C intersection A)
+ n(A intersection B intersection C)

Please pm me in case you would like to elaborate.

Hope this helps. Thanks !

The formula for 2 elements of sets is,

P(AuB)=P(A)+P(B)-P(AnB)

The formula for 3 elements of sets is,

P(AuBuC)=P(A)+P(B)+P(C)-P(AnB)-P(BnC)-P(CnA)+P(AnBnC)

4GMAT_Mumbai wrote:Hi Bubbly Rathi,

These are set theory questions. Please check your other question in which the trainer - learner - dancer has been discussed. The relationship between union, intersection and the individual sets has been provided there also.

Here goes ...

n(A union B) = n (A) + n (B) - n(A intersection B)

Note that, if there are 3 items,

n (A union B union C) =

n(A) + n(B) + n(C)
-n(A intersection B) - n(B intersection C) - n(C intersection A)
+ n(A intersection B intersection C)

Please pm me in case you would like to elaborate.

Hope this helps. Thanks !

dai ennoda post leh comment panna

This is first post in BTG I am seeing the comments in TAMIL:)

OA?

bubblyrathi,

As stuart pointed this is not a GMAT question.

Please post the question from the relevant source.