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Angela drove 212 km. Her speed was 42 km/h for about 20 min, then about 95 km/h for most of the trip, and finally about 55 km/h for the last 12 min. How long did the trip take?

Apr 3, 2021

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Let's split this into 3 parts: the 42km/h part, the 95km/h part and finally the 55km/h part.

42km/h:

Since she drove for 20 minutes (a third of an hour), and she was driving at 42 km per hour, we can just take 42 ÷ 3 = 14 km.

95km/h:

Since we don't know how long she drove, we will save this for last.

55km/h:

She drove for 12 minutes (or one fifth of an hour), and she was driving 55 km per hour, we can take 55 ÷ 5 = 11 km.

Now putting them all together, she drove a total of 212 km, and we know that she drove 14 km at 42km/h, and 11 km at 55km/h.
212 - 14 - 11 = 187 km.

Now we know how far she drove at 95km/h, and to figure out how long she drove, let's make an equation.

$$\frac{95}{60} = \frac{187}{x}$$  now cross multiply

$$95x = 11220$$

$$x = 11220 \div 95 ≈ 118.105$$

This means she drove for about 20 + 118 + 12 = 150 minutes. (150.105 approximately if decimal is needed)

Apr 3, 2021