Question

One loaf of bread and six rolls cost $1.80. At the same prices, two loaves of bread and four rolls cost $2.40. How much does one loaf of bread cost?

Answer 1

We have to find the price of one loaf of bread.

With the information we have, we can construct a system of equations.

Let B be the price of one loaf of bread and R the price of a roll.

Then, if one loaf of bread and six rolls cost $1.80, we can write:

`B+6R=1.80`

We also know that two loaves of bread and four rolls cost $2.40, so we can write:

`2B+4R=2.40`

We can solve for B with the method of elimination: we can substract the first equation from 1.5 times the second equation.

This can be express in mathematica terms as:

`\begin{gathered} 1.5(2B+4R)-(B+6R)=1.5\cdot2.40-1.80 \\ 3B+6R-B-6R=3.60-1.80 \\ (3-1)B+(6-6)R=1.80 \\ 2B=1.80 \\ B=(1.80)/(2) \\ B=0.90 \end{gathered}`

Then, we have just calculated that the loaf of bread costs $0.90.

Answer: the cost of a loaf of bread is $0.90.