How many green marbles are there?

Question

A bag contains green marbles and red marbles, 83 in total. The number of green marbles is 7 less than 4 times the number of red marbles. How many green marbles are there?

Answer 1

Hi 

Let G = Number of green marbles and R= Number of red marbles

G + R = 83 or G = 83 - R

 

G = 4R -7

Substituting 

83 - R = 4R -7

83 +7 =5R

R = 90/5 = 18

and G = 83 - 18 = 65

 

Number of green = 65

Answer 2

R + G = 83

 

G = 4R - 7

 

R + 4R - 7 = 83

 

5r = 90

 

r = 18

 

18 red, 65 green