Problem
Since 1 mi = 1760 yd, 18 mi = 31680 yd; adding the extra 900 yd gives 32580 yd in total.
Working in a single unit (yards) makes the speed easy to compute.
4.MD.A.1Analyze The UnitsThe car covers 32580 yd in 15 minutes at a steady speed, which works out to 2172 yd every minute.
A constant speed means the same number of yards is added every minute.
3.OA.A.3Identify SubproblemsDividing the 15-minute distance of 32580 yards by 15 gives the yards the car covers in one minute.
The speed never changes, so the car covers the same number of yards in each of the 15 minutes, which makes the whole trip 15 equal minute-long pieces.
Fifteen equal minute-pieces stacked together are the same as 15 times one minute's distance.
Since the total is 15 times one minute's distance, one minute's distance is that total split into 15 equal shares, because dividing undoes multiplying.
For 25 minutes, multiply the per-minute distance by 25.
More time at the same speed means proportionally more distance.
4.MD.A.2Identify SubproblemsRegroup 54300 yd into whole miles plus leftover yards: that's 30 mi 1500 yd.
Regrouping yards back into miles plus leftover yards gives the answer in the requested units.
4.MD.A.1Analyze The UnitsAt a steady speed, find how far you go in one minute, then multiply by the new minutes — same speed, more time, more distance!