Question

Bob drives 28 miles every half hour. If he drives 2 1/2 hours, how dar does he drive?

Answer 1

140 miles

1) Considering that Bob drives at a constant speed, we can write out:

hour mileage

1/2 28

2 1/2 x

2) Let's turn that Mixed Number into an improper fraction:

`2(1)/(2)=(2*2+1)/(2)=(5)/(2)`

Note that we have kept the bottom number and then multiplied that by the whole number adding it to the numerator.

2.2) Now, We can write a pair of ratios rewriting 2 1/2 as 5/2 and then cross multiplying it:

`\begin{gathered} ((1)/(2))/((5)/(2))=(28)/(x) \\ (x)/(2)=28\cdot(5)/(2) \\ (x)/(2)=(140)/(2)(*2) \\ x=140 \end{gathered}`

3) Hence, the answer is Bob drives 140 miles in 2 1/2 hours