Grade Levels: 4th Grade, 5th Grade, 6th Grade,
Topics: DecimalsFractionsPercentsRatios
Common Core State Standard: 2.MD.8, 3.OA.8, 4.MD.2, 5.NBT.7, 6.NS.3,
Knowledge and Skills:

· Can quickly estimate sums and differences of decimal numbers

Download the Teacher Guide PDF

Procedure: Distribute the handout.

There are many times that the ability to estimate a total cost of a set of items is useful, and a facility with such mental arithmetic will also improve a student’s mathematical selfconfidence.

There are several strategies that could be used to estimate such sums, such as looking for combinations that total approximately one dollar, or rounding off all numbers to the nearest 5 or 10 cents. For beginning estimators, you may wish to ask students to suggest some strategies prior to doing the activity; for students who have had some experience, you can have them do the activity first and then discuss their strategies.


Buying Supplies

It’s time to buy school supplies. Eddie needs each of the items below. He wants to get them all at one store, but he’s not sure where he should go to buy them. Can you estimate the total cost for Eddie’s supplies at each store?

Sam’s School Supplies Pete’s Pencils and Pens Mark’s Marker Market
Pencil 0.12 0.08 0.21
Ruler 0.43 0.55 0.52
Marker 0.67 0.78 0.36
Tape 0.45 0.30 0.42
Eraser 0.18 0.05 0.12
Compass 0.72 0.94 0.56
Sharpener 0.55 0.32 0.42
Glue 0.68 0.82 0.25