Math problem

Question

Benny bought 9 kg (apple + banana) for 960 dollars. how many kg apples did he buy if 1 kg apple = 80 dollars and 1 kg bananas = 140 dollars? Answer: 5 kg apple and 4 kg bananas but I want the solution

Answer 1

The solution requires two equations.

 

let x = kilograms of apples, and y = kilograms of bananas

 

1. we know that xkg + ykg = 9kg

2. from this equation, we see that ykg = 9kg - xkg

 

3. we see that $960 = $80x + $140y

 

4. we substitute the value for y from the first equation to get

$960 = $80x + $140(9kg - xkg)

then, $960 = $80x + $1260 - $140xkg

combining, we get -$300 = -$60xkg

we multiply both sides by -1 to get $300 = $60xkg

solving, we get x = 5kg, so y = 4kg