Thread: Challenging Money Math Question

How best can I approach the question below:



If Kwame had 3 cents more he would have twice as much as Ama. If he had 4 cents less, he would have the same amount.
How many cents does Kwame have?

a)4


b)7


c)11


d)14



e)none of the above

Originally Posted by KayPee

How best can I approach the question below:



If Kwame had 3 cents more he would have twice as much as Ama. If he had 4 cents less, he would have the same amount.
How many cents does Kwame have?

a)4


b)7


c)11


d)14



e)none of the above

Let be the amount that Ama has, now rewrite what you are told in terms of .

CB

Let a be what Ama has and b be what Kwame has
b + 3 = 2a
b - 4= 2a

a = b + (3/2) = a

Substituting a into equation 2
b-4 = b + 3

I am stuck and the equation doesn’t sound ok

Where did I go wrong?

Originally Posted by KayPee

Let a be what Ama has and b be what Kwame has
b + 3 = 2a
b - 4= a

See the change in red above

CB

I solved it without using a (number thatAma has) in any equation. Here is how I did it (k being the number of Kwame's cents):

k + 3 = 2(k-4)
k + 3 = 2k - 8
k + 11 = 2k
11 = k

So Kwame has 11 cents. Using the simultaneous equations method you were using you can reach the same equation.

k + 3 = 2a
k - 4 = a

Using substituion and subbing the first into the second you can get to k + 3 = 2(k-4), as named earlier. Using elimination you can subtract the second from the first and get to 7 = a. Then sub the value for a into either equation to get k = 11.

Originally Posted by Ross137

k + 3 = 2a
k - 4 = a

Using substituion and subbing the first into the second you can get to k + 3 = 2(k-4), as named earlier. Using elimination you can subtract the second from the first and get to 7 = a. Then sub the value for a into either equation to get k = 11.

Simply subtract 2nd equation from 1st: k - k + 3 - (-4) = 2a - a
So 7 = a

Yep - that's what I meant by elimination