Post mathematic related questions here

[rst]

A cat chases a rat. For every 5 leaps of the rat , the cat takes 3 leaps, but the 2 leaps of the cat are the same as 3 leaps of the rat. Compare the speeds of the cat and the rat

a)4:5
b)12:13
c)16:15
d)none of these

 

[rst]

Ans is 9:10

 

[sohan_92]

Ans is 9:10

care to explain?

 

[rst]

Here distance of leaps of cat and rat are not same
clearly the 2 leaps of the cat are the same as 3 leaps of the rat
Let distance of rat leap be x

then distance of cat's leap = 3x/2 =1.5X

then speed ratio =(1.5x*3)/(x*5)= 4.5x/5x

9/10

 

[rst]

A bike is sold by an automobile agency for rupess 19200 cash or for 4800 cash downpayment together with 5 equal monthly installment if rate of interest charged by the company is 12% per annum .find the amount of the installment

 

[anirbandd]

the question that follows is quite common in Combinatorics and all the maths books arrive at the answer through a single method. i have never seen any variations so far.
however, that method of arriving at the answer is not how you would deal with the problem in real life.

how would YOU solve it?

A class contains 12 boys and 10 girls. From the class 10 students are to be chosen for a competition under the condition that atleast 4 boys and atleast 4 girls must be represented. The 2 girls who won the prizes last year should be included. In how many ways can the selection be made?

Instead of giving a numeric answer, i would like to know how you approach the problem..

 

[thetechfreak]

I guess the general approach could be doing a combination keeping the 2 girls fixed and selecting 2 more from the remaining 8 girls. Boys can be selected with 12C4. Multiplication of both the results should give the needed output.

 

[anirbandd]

That problem was the end of this thread, wasnt it