# 7th grade algebra word problem

#### coppercat30

##### New member
I cannot figure out how to solve the following question-

A jar contains red, blue and yellow marbles. The # of red is 10 more than the yellow, and the blue is double the yellow. If the probability of choosing a yellow marble is 1/5 how many marbles are in the jar?

This is as far as I can go: r+10=y 2y=b

#### mmm4444bot

##### Super Moderator
Staff member
coppercat30 said:
The # of red is 10 more than the yellow

r+10=y

This equation needs fixing; r is already the bigger number.

Red is bigger than yellow by 10; if you want to write an equality, then you need to add 10 to the smaller number.

r = y + 10
The ratio of yellow marbles to the total of all marbles is 1 to 5.

y/(r + b + y) = 1/5

Substitute your expressions for r and b into the proportion above, and solve for y.

After you determine the number of yellows, calculating the reds and blues is easy because you already wrote formulas for them:

r = y + 10

b = 2y

At this point, you can answer the exercise because the question asks for r + b + y.

If you need more help, please share what else you've come up with, thus far.

Cheers ~ Mark