Speed Problems: Conversion of Speed and Time Units
The red kangaroo hops across 120 meters in five seconds. What is the speed of the kangaroo in kilometers per minute?
Incorrect.
[[snippet]]
Incorrect.
[[snippet]]
Incorrect.
You must have missed a decimal somewhere . . .
[[snippet]]
Correct.
First of all, assign each of the values in the question to the
appropriate cell in the speed table. Then, convert the units using the
replace with an equivalent principle.
Replace the word
meters with the
equivalent $$\times \frac{1}{1{,}000}$$ kilometers.
Go on to replace the word
seconds with the
equivalent $$\times \frac{1}{60}$$ minutes.
|
speed
| time | distance |
| ? |
$$5$$ seconds
|
$$120$$ meters |
| ? |
$$5\times\frac{1}{60}$$ minutes |
$$120\times \frac{1}{1{,}000}$$ kilometers |
Simplifying the time and distance gives $$\frac{5}{60} = \frac{1}{12}$$ minutes and $$\frac{120}{1{,}000} = \frac{3}{25}$$ kilometers.
Finally, calculate the speed.
>$$\displaystyle \text{Speed} = \frac{\text{Distance}}{\text{Time}}$$
>>$$\displaystyle = \frac{\frac{3}{25} \mbox{ kilometers}}{\frac{1}{12} \mbox{minutes}}$$
>>$$\displaystyle = \frac{3}{25} \times \frac{12}{1} \mbox{ kilometers per minute}$$
>>$$\displaystyle = \frac{36}{25} \mbox{ kilometers per minute}$$
>>$$\displaystyle = 1.44 \mbox{ kilometers per minute}$$
Incorrect.
[[snippet]]