Problem
Speed is distance over time
A storm covers a known distance, and its distance-per-hour rate is given. We need how long the journey takes, in hours and minutes.
Ratios
Your answer
How to solve
Strategy Analyze the Units — Read the rate as a sentence about division, then turn that sentence around. The answer comes out as a decimal number of hours, which then has to be read back into minutes.
1STEP 1
Read what the rate says
The rate of distance to time being 144 means the storm covers 144 kilometers in each hour.
(rate) = (distance) ÷ (time)
144 km every hour.
6.RP.A.2Analyze The Units2STEP 2
Turn the sentence around
If the rate is distance over time, then time is distance over the rate.
324 ÷ 144 = 2.25
The journey takes 2.25 hours.
6.RP.A.3Work BackwardsThe time taken is the distance divided by the rate.
Why?
A rate of means the storm covers kilometres in each hour, so the whole distance is that many equal hourly stretches.
🧱Multiplication as equal groupsa times b means a equal groups of b — it is just repeated adding of the same amount.
Why?
Asking how many of those stretches fit into is the division that undoes the multiplying.
🧱Inverse operationsSubtraction undoes addition and division undoes multiplication — they reverse each other.
3STEP 3
Read the decimal part as minutes
The 0.25 of an hour is a quarter of 60 minutes.
0.25 × 60 = 15
That is 2 hours 15 minutes.
6.RP.A.3Identify SubproblemsAnswer
2 hours 15 minutes
Multiply back: 144 × 2.25 = 324 km, the distance given.
Takeaway
A rate is a division sentence -- turn it around and it gives back whichever quantity is missing.
- Read what the rate says
- Turn the sentence around
- Read the decimal part as minutes