An executive bought 300 stamps for $73.80. The purchase included 15 cent stamps, 20 cent stamps, and 40 cent stamps. The number of 20 cent stamps is four times the number of 15 cent stamps. How many 40 cent stamps were purchased?
I need to do this in a chart form and have already set it up but I am lost on what to do next.
number of 15 cent stamps --- x
number of 20 cent stamps --- 4x
number of 40 cent stamps ---- 300 - 5x
15x + 20(4x) + 40(300-5x) = 7380
solve for x
plug that into 300-5x
Chart form ???
What grade level is this ?
To solve this problem, let's complete the chart you have set up step by step:
Let's assume the number of 15 cent stamps is x.
According to the problem, the number of 20 cent stamps is four times the number of 15 cent stamps. So, the number of 20 cent stamps would be 4x.
Now, the number of 40 cent stamps can be calculated by subtracting the total number of 15 cent and 20 cent stamps from the total number of stamps, which is 300.
So, the number of 40 cent stamps would be 300 - (x + 4x) = 300 - 5x.
We are also given that the total cost of the stamps is $73.80. The cost of the 15 cent stamps can be calculated by multiplying the number of 15 cent stamps (x) by $0.15. Similarly, the cost of the 20 cent stamps can be calculated by multiplying the number of 20 cent stamps (4x) by $0.20. And the cost of the 40 cent stamps can be calculated by multiplying the number of 40 cent stamps (300 - 5x) by $0.40.
So, the equation representing the total cost is:
0.15x + 0.20(4x) + 0.40(300 - 5x) = 73.80.
Now, you can solve this equation to find the value of x, which represents the number of 15 cent stamps.
Once you find the value of x, substitute it back into the expression for the number of 40 cent stamps (300 - 5x) to calculate the number of 40 cent stamps.
I hope this guidance helps you solve the problem using the chart you have set up.