an orange has 20 fewer calories than a banana. If 7 bananas have the same number of calories as 9 oranges, how many calories are in a banana?

Question

an orange has 20 fewer calories than a banana. If 7 bananas have the same number of calories as 9 oranges, how many calories are in a banana?

Answer 1

Let X be the number of calories in a banana, and Y be the number in an orange.

7X = 9Y
7X - 9Y = 0
X - Y = 20
9X - 9Y = 180
2X = 180
X = 90
Y = X -20 = 70

Answer 2

To solve this problem, we can use algebraic equations. Let's represent the number of calories in a banana as "B" and the number of calories in an orange as "O."

Given that an orange has 20 fewer calories than a banana, we can set up the equation:

O = B - 20 (Equation 1)

We also know that 7 bananas have the same number of calories as 9 oranges. So we can set up another equation:

7B = 9O (Equation 2)

Now we can substitute Equation 1 into Equation 2 to solve for B:

7B = 9(B - 20)

Multiply through the parentheses:

7B = 9B - 180

Subtract 9B from both sides to isolate the B term:

-2B = -180

Divide both sides by -2:

B = -180 / -2
B = 90

Therefore, there are 90 calories in a banana.