Simple Quick Math Question

Question

I lend a friend $70. He invests $50 in a stock and makes $30 profit. He then invests the other $20 into a stock that profits him $100. How much does the friend have left in profit after paying the original loan?

Answer 1

$70 loan used to invest $50 in stock with a $30 profit and $20 in another stock with $100 profit

How much profit is left after repaying his friend the $70 loan?

total profit was 30+100 = $130. After repaying the $70, he still has the full $120 profit

this seems like a trick question, as it's tempting to say only 130-70 = $60 profit left. But that ignores the $50+$20 that got invested. Use it to repay the $70 loan and $130 profit is still left over.

this assumes the friend doesn't charge interest. Friends usually don't charge interest, although when he finds out you made $130 profit with his money, he might wonder why you didn't offer to share some of it with him, as he risked you losing some of it, and risked not getting the loan back, had the stock prices gone down, instead of up.