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WRITTEN MULTIPLICATION
Karl runs 3 laps around the park. One lap is
1,230 m long. How many metres does Karl
run on each occasion he goes running?
m
? m
3 \latex{ \times } 1,230 m =
We can count in words the following way:
3 \latex{ \times } 1,230 = 3 \latex{ \times } 1,000 + 3 \latex{ \times } 200 + 3 \latex{ \times } 30 = 3,000 + 600 + 90 =
=
m
Large numbers are easier to multiply in writing.
Make an estimate before completing the written multiplication.
Estimate with the four digit values of the factors rounded to hundreds:
1,230 \latex{ \approx } 1,200, 3 \latex{ \times } 1,200 =
factors
1
2
3
0
·3
product
\latex{ \bullet } 3-times 0 units =
\latex{ \bullet } 3-times 3 tens =
\latex{ \bullet } 3-time 2 hundreds =
\latex{ \bullet } 3-times 1 thousands =
units.
tens.
hundreds.
thousands.
Check the solution with addition.
The product
. Is appropriate for the estimate.
=
m
Karl runs
metres on each occassion he goes running.
Check:
+
{{exercise_number}}. Do the written multiplications. Estimate the product first by rounding the factors to hundreds. Check your calculations with written addition.
E:
E:
E:
E:
C:
C:
C:
C:
4123·2
1221·4
2303·3
3012·2
What is seven times 1,371?
Estimate: 1,371 \latex{ \approx } 1,400,
1,400 \latex{ \times } 7 =
\latex{ \bullet } 7-times 1 units =
tens (t). Write down the
\latex{ \bullet } 7-times 3 h =
\latex{ \bullet } 7-times 1 T =
units (u).
\latex{ \bullet } 7-times 7 tens =
t,
and add the 4 hundreds (h) to the product of the hundreds.
h, plus 4 h is
h. Write down the
h,
and add the 2 thousands (T) to the product of the thousands.
T, and 2 T is
T.
The product is
. It corresponds to the estimate.
T
h
t
u
1
3
7
1
·7
{{exercise_number}}. Complete the written multiplications. Estimate the product first with factors rounded to hundreds.
a)
b)
c)
d)
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
E:
325·3
1418·2
2124·4
3126·3
1060·3
3374·2
2091·4
1283·3
531·2
2802·3
943·2
1523·3
743·9
658·6
2607·3
852·4
{{exercise_number}}.
a) Colour the ones that belong together the same colours.
b) Calculate the exact products.
394 \latex{ \times } 9
806 \latex{ \times } 4
586 \latex{ \times } 3
294 \latex{ \times } 7
873 \latex{ \times } 6
\latex{ \approx } 2,100
\latex{ \approx } 3,200
\latex{ \approx } 3,600
\latex{ \approx } 1,800
\latex{ \approx } 5,400
{{exercise_number}}. Do the written multiplications. Estimate with factors rounded to hundreds first. Check your answer with written addition.
827 \latex{ \times } 7
1,506 \latex{ \times } 6
3,429 \latex{ \times } 2
2,079 \latex{ \times } 4
1,637 \latex{ \times } 3
{{exercise_number}}. Calculate the products, then colour them the right colour in the table.
2
6
3
1
5
5
2
3
4
0
1
0
4
3
7
4
0
1
3
5
6
3
7
3
4
5
2
1,205\latex{ \times }3
789\latex{ \times }6
2,617\latex{ \times }2
509\latex{ \times }7
863\latex{ \times }4
{{exercise_number}}. Complete the operations. Write the products in the right sets.
E:
E:
E:
E:
E:
E:
479·9
2653·2
615·7
707·8
1908·4
1875·3
odd
greater than 5,000
{{exercise_number}}. Write the products in the figure, so the arrows point to the larger number.
689 \latex{ \times } 4
517 \latex{ \times } 5
1,402 \latex{ \times } 3
298 \latex{ \times } 9
721 \latex{ \times } 6
{{exercise_number}}. Complete the calculations. Pay attention to the order of operations!
a)
b)
4,625 \latex{- } 1,283 \latex{ \times } 2
1,709 \latex{\times } 3 + 2,586
(579+1,058) \latex{ \times } 6
(4,413\latex{ - }2,763) \latex{ \times } 4
1,842 \latex{ \times } 5 \latex{ - } 462 \latex{ \times } 3
648 \latex{ \times } 3 + 1,053 \latex{ \times } 4
{{exercise_number}}. Solve the following exercises.
- Every volume of a 4 volume book series costs 5,000 ¢. How much does the whole series cost?
- Zoe got sick, so her mom cancelled her lunch for 1 week. How much less will she have to pay next month, if one lunch costs 661 ¢?
- How much does lunch in your school cost? Find out. Calculate how much you would (have to) pay for lunch for a week.
- Third of the visitors to the weeklong exhibit went on the weekend. How many visitors were there, if 847 people went on the weekend?
- There are 8 pens in a box. One pen is 140 ¢. How much do 3 boxes cost?
- Mom bought 3 red and 2 black cardboard sheets to make a costume. How much did it cost, if red cardboard cost 216 ¢ and black costs 160 ¢ a sheet?
- They laid 156 four person, and 53 six person tables at the spring ball. How many people had dinner at the ball at the most?
{{exercise_number}}.
At least:
, at most:
d) Mary divided a number by 5, but did the calculation wrong. The result was 120 more than
if she had done it correctly. Which number did Mary divide if she got 1546?
c) I’ve thought of a four digit number. I divided it by three, then divided the result by three
and so on, until I got 248. Which number could have I thought of?
a) I’ve thought of a number, when dividing it by 6 I got 743. Which number did I think of?
b) I’ve thought of a number, I added 325 to half of it, and I got 2498. Which number
did I think of?
{{exercise_number}}.
a) I multiplied 784 by something, the result was 2,352. What
did I multiply it by? Use trial and error.
b) Fill in the missing digits. Use trial and error.
1573·
6292
9630
961·
0·7
4
1
·2
8
49
8
7
2
784·
2352
{{exercise_number}}. Fill in the tables, estimate with factors rounded to hundreds.
factors
estimated result
product
factors
estimated result
product
489 and 7
1,563 and 6
829 and 4
\latex{ \approx }
\latex{ \approx }
\latex{ \approx }
527 and
1,793 and
2,067 and
\latex{ \approx } 4,200
\latex{ \approx } 5,400
\latex{ \approx } 3,000
3,162
5,379
4,134
{{exercise_number}}. There are 8, 275 ml soap dispensers on each floor of a 4 storey office building.
- How much soap is needed to fill up all the dispensers on one floor?
- How much soap is needed to fill up all the dispensers in the office building?
{{exercise_number}}.
- 345 kg of bananas and four times as many oranges arrived at a store. How many kilograms of fruit arrived altogether?
- Dean goes on trip to the mountains with his parents and his brother. They bought insurance for the trip. It costs 415 ¢ a day for adults and 245 ¢ a day for children. How much is the insurance for the family for a week?
{{exercise_number}}. Alex spent half of his money, he has 2,475 ¢ left.
- How many ¢ did Alex spend?
- How much money did Alex have?
{{exercise_number}}.
- Four times which number is 567 more than three times that number?
- Mark bought 8 packs and Zoe bought 7 packs of crackers. How much did they each pay, if Zoe paid 163 ¢ less than Mark?
