111

Work out these costs.

1 Buy 10 each of the:

a iceblocks. b fortune cookies. c pinatas. d hats.

____________ ____________ ____________ ____________

2 Buy 20 each of the:

a umbrellas. b candles. c hats. d masks.

____________ ____________ ____________ ____________

3 Buy 30 each of the:

a lanterns. b leis. c masks. d balloons.

____________ ____________ ____________ ____________

4 Buy 50 each of the:

a umbrellas. b iceblocks. c candles. d balloons.

____________ ____________ ____________ ____________

Money multiplicationMoney multiplicationThe Santos are planning a big party with lots of food and prizes galore.

29c each

63c each 17c each

16c each

84c each

45c each

76c each

30c each

32c each

98c each

ACMNA100 Number and place value • Solve problems involving multiplication of large numbers by one- or two-digit numbers using efficient mental, written strategies and appropriate digital technologies.

corporate climbingLab 5Lab 5

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Working with money

112

TrialanderrorSam bought 3 of one item and four of another. The total cost was $3.91.

What did he buy? and

Use the prices on page 111.

1 Use the extended form to work these.

Find the cost of:

a 5 iceblocks. b 7 party hats.

c 8 leis. d 6 masks. e 8 cookies.

2 Use the contracted form to work these.

Find the cost of:

a 3 pinatas. b 9 candles. c 4 umbrellas. d 7 lanterns.

e 8 masks. f 9 balloons. g 5 leis.

3 Read all your answers. Circle any that don’t make sense. Rework them.

Did your answers change? ______________

Multiplication algorithmsMultiplication algorithms

MultiplicationExtendedform

68c π7 56 (7π8) +420 (7π60)476c=$4.76

Contractedform568c

π7476c=$4.76

tradenumbergoeshere

MoneyRememberthesigns 47cπ30 =1410c =$14.10 58cπ8 =464c =$4.64

29cx 5

(5x9)(5x20)=$

98cx 3

4= $

2

32cx 7

ACMNA100 Number and place value • Solve problems involving multiplication of large numbers by one- or two-digit numbers using efficient mental, written strategies and appropriate digital technologies.

Working with money

!

113

Multiplication algorithmsMultiplication algorithms

Challenge!

Three-digit multiplicationThree-digit multiplication1 a b c

2 Circle the errors. Write the correct numerals in red.

3

4

π7

7 0

8 356

4 9π4

10 2

9 463

7 8π6

1 5

0 694

8 7

a 6 7 π 9 6 0 6

b 8 1 π 5 4 8 6

c 9 5 π 5 4 2 5

d 4 6 π 4 1 7 4

e 3 0 π 6 1 8 6

a 7 2 3 π 3

b 8 1 5 π 6

c 9 3 6 π 4

d 2 6 8 π 7

e 5 1 9 π 8

f 4 5 7 π 5

g 6 4 1 π 9

h 3 9 2 π 2

a 1 0 3 π 7

b 9 7 0 π 3

c 5 0 8 π 8

d 4 6 0 π 9

e 6 9 0 π 6

f 3 0 2 π 0

g 8 9 0 π 5

h 7 5 0 π 4

Multiplying3-digitnumbers

7 6 2 π 5 3 8 1 0

3 1

a 3 7 2 5 0 6 1 4 9 8 π 7

b 6 0 2 9 4 7 5 1 3 8 π 9

Becarefulwithzeros!

ACMNA100 Number and place value • Solve problems involving multiplication of large numbers by one- or two-digit numbers using efficient mental, written strategies and appropriate digital technologies.

3-digit algorithms

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114

Problem solvingProblem solvingKeeping up supplies

ACMNA100 Number and place value • Solve problems involving multiplication of large numbers by one- or two-digit numbers using efficient mental, written strategies and appropriate digital technologies. ACMNA106 Money and financial mathematics • Create simple financial plans.

Youcanuseacalculator.

1 Mrs Jackers needs 70 to 100 new stickers for her class. She can spend $20. She needs three different designs. Each design has 10 stickers on a card.

Help her make the decision and spend as close to $20 as possible. Seasons $2.40 Musical $2.60 Positives $3.25 Sports $1.90 Reminders $2.50

Show your working.

2 Jacko wants to keep a supply of cards on hand for special events in his family. He has $50 to spend on cards and wants four different designs. Help him to spend as close to $50 as possible and total the amount he spends.

Desert Birds $2.70 ea Fuzzies $3.65 ea Far Out $2.25 ea Reef Life $1.90 ea Champions $5.20 ea

Show your working.

3 Handyman Alan needs to upgrade his stock of nails and screws for his handyman jobs. He can spend $100. He needs a few packs of each size of nails and screws. How many of each size can he buy to spend all, or almost all, of his money?

50 mm nails $2.40 35 mm screws $3.10 75 mm nails $2.80 40 mm screws $3.45 100 mm nails $2.95 50 mm screws $3.60

Show your working.

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