Writing expression from Word Problems

Question

The Roberts family is taking a train trip. The cost of an adult ticket is twice the price of a child’s ticket. A child’s ticket sell for an unknown cost. Write an expression for the cost of the Roberts family (2 adults and 3 children) to ride the train.

Answer 1

If an adult ticket is twice the price of a child's ticket, this means that, with a=adult ticket and c=child ticket, a=2c. Because the Roberts family is 2 adults and 3 children, we will need 2a, which equals 4c (multiplying by 2) plus 3c for 3 children, so 4c + 3c = 7c, or 7 times the price of a child's ticket c.

Answer 2

Hi Stephanie,

Let's break your problem into parts, which will help us to write an expression.

"A child’s ticket sell for an unknown cost."

When we don't know the value of something, we use a variable to represent it. Let's use c to represent the cost of the child's ticket.

"The cost of an adult ticket is twice the price of a child’s ticket."

Let's use a to represent adult ticket, as we do not know that cost either.

a = 2c

"Write an expression for the cost of the Roberts family (2 adults and 3 children) to ride the train."

We would start with 2a+3c. However, we can substitute 2c any place in the expression where we see a. (We noted above that a = 2c.)

The new expression is 2(2c )+3c, which can be further simplified to find a final answer.

I hope this explanation is helpful! If you found it useful, please upvote it.