Question

You and your friend each have some pennies. If you give your friend 1 penny, then you and your friend

will have the same number of pennies. If your friend gives you 1 penny, then you will have twice as many
pennies as your friend. How many pennies did you each start with?

Answer 1

You have 3 pennies and your friend has 1 penny

Explanation:

The given parameters are;

Let friend A = you

friend B = Your friend

The number of pennies with friend A when he gives friend B 1 penny = Equal number of pennies between friend A and B

The number of pennies with friend A when he is given 1 penny by friend B = 2 times the number of pennies with friend B

Let the number of pennies with friend A = X and the number of pennies with friend B = Y, therefore, we have;

X - 1 = Y + 1.....................(1)

X + 1 = 2 × Y...................(2)

Subtracting equation (1) from equation (2), we get;

X + 1 - (X - 1) = 2·Y - (Y - 1)

X - X + 1 + 1 = 2·Y - Y + 1

2 = Y + 1

Y = 2 - 1 = 1

Y = 1

From equation (1), X - 1 = Y + 1 gives;

X - 1 = 1 + 1

X = 1 + 1 + 1 = 3

Friend A has 3 pennies and friend B has 1 penny.

Therefore, you have 3 pennies and your friend has 1 penny