Page 18 - 01-Yr5_Front cover-ccp.indd

20
• Best ways • • •
There ore many different ways
~=M•li1"10~ to work out difficult multiplications. x 27
34
34
34 x27
I \
x 27
PAGE 30 x20 x 7 -m (34x7} -a4cJ (34 x 1 O)
34
34
+ 680 (34 x 20)
340 (34x10)
68o 238 918 +238 (34x7)
,--
,--
\68/ 918
+ 238
918 rn
[D Decide the best way to find the products
a 32 x 32 = 1 024 33 x 31 = 1023
of these. Show all your workings-out.
a 45x35 b 31x12 c16x45
d 57 x 21 e 72 x 26 f 69 x 18 34 x 30 = 1020 35 x 2q = 1015
m Check each product in II] by multiplying
in reverse order. For example, for a you will b The pattern in the products: they
calculate 35 x 45.
decrease by 1 , 3, and then 5.
@] Decide the best way to solve these problems.
The product is decreasing each
a A day trip by coach ta Blackpool costs £27
for adults and r16 for children.
If 30 adults and 13 children go, what will be time. The amount by which the
the total cost of fores?
@] product decreases is 2 more each
b Sarah works a 38-hour week at a Blackpool hotel Do the some for other pairs of 2-digit starting numbers.
and has 6 weeks holiday each year. Explain the pattern you find each time. time, starting with 1.
How many hours does she work
in a complete year?
c 36 x 28 = 1 008 37 x 27 = qqq
c A stick of rock is 28 cm long. CHALLENGE
What length of rock would be needed • Use each of these keys S (_gJ W ~ 1111
to make a box of 48 sticks? once each time. 38 x 26 = q88 3q x 25 = q15
[3J If 25 is the 5th square number,
•Then show that you con make 12 different products
what is the 42nd square number? by multiplying pairs of 2-digit numbers together. d Practical: check the predicted
Now try page 31. answers inc are correct.
m
rn [gJ
a 1575 b 372 c 720 e 1872 f 1242 a 27 x 28 = 756 26 x 2q = 754 25 x 30 = 750 24 x 31 = 744
The pattern in the products: they decrease by 2, 4 and then 6.
[gJ The product is decreasing each time. The amount by which the product
decreases is 2 more each time, starting with 2.
Practical: check each answer in DJ by multiplying in reverse order. 23 x 32 = 736 22 x 33 = 726 21 x 34 = 714 20 x 35 = 700
00 b 30 x 26 = 780 31x25 = 775 32 x 24 = 768 33 x 23 = 75q
The pattern in the products: they decrease by 5, 7 and then q_
The product is decreasing each time. The amount by which the product
a 30 x 27 = 810 and 13 x 16 = 208 so total cost is £810 + £208 = £1018
decreases is 2 more each time, starting with 5.
b 52 - 6 = 46 weeks so 46 x 38 = 1748 hours a year 34 x 22 = 7 48 35 x 21 = 735 36 x 20 = 720 37 x 1 q = 703
c 48 x 28 = 1344 cm
Challenge
~ Open: do the 52 x 83 = 4316 25 x 83 = 2075 85 x 32 = 2720
42 x 42 = 1764 same for other 52 x 38 = 1q16 25 x 38 = q5o 82 x 35 = 2870
pairs of two-digit 58 x 32 = 1856 28 x 35 = q8o
starting numbers 58 x 23 = 1334 23 x 85 = 1%5
and explain their 53 x 82 = 4346
patterns. 53 x 28 = 1484