Porportional Equation

Question

The proportion of red marbles to blue marbles in a jar is 2 to 5. If there are 35 blue marbles in the jar, how many red marbles are there.

Answer 1

r / b = 2 / 5

2 / 5 = r / 35

Can you solve for r and answer?

Answer 2

Ratio of 2 to 5 means that 2/7 of them are red and 5/7 of them are blue

X is the number of marbles altogether

5/7 of X is 35

5/7 X = 35 <--- 5/7 of them are blue; That is 35 of them (or 5/7 of them) are blue

X = 35 * 7 / 5 <--- solves the equation by multiplying by the reciprocal 7/5

x = 49

There are 49 marbles altogether

There are 14 red marbles

14/49 = 2/7

35/49 = 5/7

YES, it checks!