Question

A bag contains blue marbles and red marbles, 75 in total. The number of blue marbles is 5 more than 4 times the number of red marbles. How many blue marbles are there?

Answer 1

There are 61 blue marbles

Solution:

Let "b" be the number of blue marbles

Let "r" be the number of red marbles

Given that bag contains blue marbles and red marbles, 75 in total

number of blue marbles + number of red marbles = 75

b + r = 75 -------- eqn 1

The number of blue marbles is 5 more than 4 times the number of red marbles

number of blue marbles = 5 + 4(number of red marbles)

b = 5 + 4r ------- eqn 2

Let us solve eqn 1 and eqn 2

Substitute eqn 2 in eqn 1

5 + 4r + r = 75

5 + 5r = 75

5r = 75 - 5

5r = 70

r = 14

From eqn 2,

b = 5 + 4(14) = 5 + 56 = 61

b = 61

Thus there are 61 blue marbles