A fruit vendor bought 36 pineapples for $30. He sold some at $1.29 each and the rest at $1.09 each, thereby gaining $13.64. How many did he sell at each price? :confused:

Hi,
Let x = number sold for 1.29
Then (36-x) = number sold for 1.09

If he gained $13.64, it means he made a total of $43.64 (add 30 to 13.64)

So:
1.29(x) + 1.09(36-x) = 43.64

multiply it out:
1.29x + 39.24 - 1.09x = 43.64

Combine terms:
0.2x + 39.24 = 43.64

Subtract:
0.2x = 4.4

Then, divide by 0.2
x = 22
Then, 36-22=14
So,
y = 14
That is 22 sold for 1.29
and 13 sold for 1.09
You can check the answer by: 1.29(22) + 1.09(14) = 43.64
The trick here is "gained", so adding the gain to what he paid would be what the tolal is.
Best wishes.

Thanks for your help :D