Robert gave one-half of his marbles to Dean. Then he gave two-thirds of the remaining ones to Mark. If he ended up with 10, how many did he have when he stsrted?
1 answer
The 10 marbles he had left would be the same as one-third, so multiply by 3 to get how many marbles he had after he gave half of them to Robert. 10x3=30. Since 30 is half of what he orginally had, multiply by 2. 2x30=60. He started with 60 marbles.