Question

Martin spent $300 from his savings account on a new bike. He also deposited $300 in his savings account that he earned from selling his used textbooks. Which integer represents the change in Martin's savings? A) $100 B $0

C. -100$ D. -$200​

Answer 1

B

Explanation:

a money account works in the same way as real things we can touch.

so, when I have 300 apples at a place (e.g. a grocery store), then I take away 300 apples, and then put again 300 apples there - how many apples will be there at that moment ?

we had 300 and took away 300.

300 - 300 = 0

at that moment we have 0 apples.

but then we put again 300 apples there.

0 + 300 = 300

so, we end up with 300 apples. the same number we started with.

and the same way for the savings account.

he takes out $300.

that means he has now $300 less on his account.

and then he adds $300.

so, he added exactly the same amount as he took out earlier, which means nothing else than that he undid his earlier action regarding his bank account.

so, his balance is now exactly the same as before he did the first transaction.

therefore the change is exactly : $0