Maps with decimal distances

A missing-part problem asks your child to think in two moves. The whole is known, some parts are known, and one part is not. Adding the known parts and subtracting from the whole is the cleanest route.

On the first map, the four known legs are 9.10, 7.95, 5.2 and 12.1 km. The answer page rewrites the last two as 5.20 and 12.10 before adding, which is the habit to copy: equal decimal places, then 34.35 km. Taking that from 40.9 km, written as 40.90, leaves 6.55 km. The second map is a plain sum of decimal distances: 9.2 + 19.7 + 8.4 + 12.7 = 50.0 km, a round total that makes a nice surprise.

On the standards side, this is 6.NS.B.3: adding and subtracting multi-digit decimals fluently with the standard algorithm.

Put a finger on Selma and let your child trace the whole route to Decatur. "How long is the trip?" They should find 40.9 km in the question, not on the map.

The likely slip comes next: adding all five numbers, the 40.9 included, and getting 75.25 km. Ask, "Is 40.9 a road or the whole trip?" Another one is writing 34.35 under 40.9 by their last digits, so the 5 hundredths sit under the 9 tenths. Writing 40.90 fixes the columns.

For the Gila Bend map, invite a check: does 50 km look right? A quick estimate of 9 + 20 + 8 + 13 = 50 says yes. Page 1 also has a small typo in the first question, assum for assume.

Pick three stops on a map app before the next drive. Your child writes each leg with one decimal place, in miles or kilometers, adds them, and compares the total with what the app says for the full trip.

The car's trip odometer is another clue. Reset it at home, read it at the store and again back home, and ask how long the return leg was.

Millions to Measure by David M. Schwartz explains why meters and kilometers exist at all, a good companion for a page measured in km.

End on what they managed: "You found a road nobody had measured for you." The next sheet, Multiplying decimals, starts a new unit where the decimal point moves in a new way.