Estimating sums, differences, products and quotients by rounding or using nearby easy numbers, and using an estimate to tell whether an answer makes sense.
Round to numbers that are easy to work with, then do the math in your head. For division, change the first number to one the divisor goes into: 4,215 ÷ 7 is about 4,200 ÷ 7 = 600.
estimatea close answer found with easier numbers
roundchange a number to a nearby ten, hundred or thousand
compatible numbersnumbers easy to divide in your head
reasonablemakes sense, close to the estimate
Watch for: Rounding one number and not the other. Rounding 4,215 ÷ 7 to 4,000 ÷ 7, which doesn't divide evenly. Accepting an answer ten times too big because the digits look right.
At home: At the store, estimate the total of three items before checkout, then compare with the receipt.
Sample sheet and answer key
Luna's Space Adventure
Grade 5 · Estimating with all four operations · 5.3A
NameDate
Astronaut Luna is exploring a far-off corner of space. Solve each problem to help Luna's mission go smoothly!
Something wrong with this sheet? A wrong answer, a hard-to-read picture? Report it
New problems every time, three levels (gentle, core and stretch), themes to pick from, a second page if you want one. Each sheet comes with an answer key and a one-page guide for grown-ups.
