Question 825515
A eats 3 apples in 5 days, or 3/5 apple per day.<P>
B eats 6 apples in 4 days, or 6/4 apples per day.<P>
Together they eat 3/5 + 6/4 = 12/20 + 30/20 = 42/20 = 21/10 apples per day.<P>
They eat 21 apples in 21 / (21/10) = 21/1 * 10/21 = 10 days.