Rounding & Estimating
Story Problems
Multiplication Strategies
100
60 x 50 = 3,000
40 x 60 = 2,400
100
Mr. Saunders ordered 13 boxes of pencils. Each box holds 35 pencils. How many pencils does he get? Use partial products to solve.
(30 + 5) x (10 + 3) =
30 5
10 300 50
3 90 15
300 + 90 + 50 + 15 = 455
100
Basic Fact: 8 x 2 = 16
Adding Zeros back in: 3 zeros in factors = 3 zeros in product
800 x 20 = 16,000
200
How would you round each problem? Choose from the options below:
25 x 40 30 X 30 50 X 20
23 X 38 ____________
31 X 32 ____________
46 X 18 ____________
39 X 21 ____________
200
Mrs. Tinholt has 22 pumpkins. Ms. Klein has 13 times as many pumpkins as Mrs. Tinholt. How many pumpkins does Ms. Klein have?
22 x 13 = 286 pumpkins
200
DAILY DOUBLE!!
300
Miss Gipe's class went on a field trip. There are 28 students. The field trip costs $26 per student.
Round each factor to estimate the total cost of the field trip.
Use compatible numbers to estimate the total cost of the field trip.
Which estimate is the better estimate. Why?
Estimation with Rounding: 30 x 30 = 900
Estimation with Compatible Numbers: 30 x 25 = 750
The compatible numbers are closer to the original factors so that is a better estimate.
300
Mrs. Allen places 4 orders for school t-shirts. Each order has 17 boxes of shirts and each box holds 19 shirts. How many t-shirts does Mrs. Allen order in all?
17 x 19 = 323 shirts PER ORDER
4 orders:
323 x 4 = 1,292 shirts IN TOTAL!
300
1800
720
100
40
=2,660
400
27 x 19 =
30 x 20 = 600
400
A music stores sells CD players. They sold 12 blue CD players and 27 red CD players. Each CD player costs $18.
Estimate the cost of all the CD players sold.
What is the exact cost?
400
DAILY DOUBLE!!
(10 + 5) x (30 + 2)
(10 x 30) + (10 x 2) + (5 x 30) + (5 x 2)
500
1200
80
30
2
= 1312
500
It's moving day for Chi Chi! Chi Chi packs 24 boxes with 20 raisins in each box. Her mom packs 37 boxes with 25 raisins in each box. Who packed more raisins? How many more raisins?
Chi Chi: 24 X 20 = 480 raisins
Chi Chi's Mom: 37 X 25 = 925
The difference 925
- 480
445
500
DAILY DOUBLE!!
