Page 84 - Math Smart - 7

Check My
Understanding

O A bee colony produced 0.272 kg of honey. The beekeeper collected 91 g of the honey. How
many kilograms of honey remains?
© The mass of a baby elephant was 206.99 kg. After two years, her mass increased by 108.95 kg.
Find the mass of the elephant after two years.
© Leo had a piece of rope 35.15 m long. He cut the rope into two pieces. If the length of one piece
of rope was 13.59 m, what was the length of the other piece of rope?
O The length of each side of a regular polygon is 6.3 mm. Its perimeter is 31.5 mm.

a) Find the number of sides the polygon has.
b) Name the polygon.

4.2.2 Multiplying whole numbers and

decimals by 10, ICQ and 1000

Investigate!
PAIR WORK
An elephant eats 0.236 tonne of food per day. How many tonnes will
the elephant eat in 10 days? We need to multiply 0.236 by 10.
Remember to fill in any
Study the table to see what happens when we multiply a decimal
spaces to the left of the
number by 10.
decimal point with zeros.
This gives the correct
itiv/ r • II
place value to the rest of
X 10 0 • ^2 /3 x6
the digits. 2 • 3^ 6^

When we multiply 0.236 by 10, the 2 digits moved from the tenths
column to the units column.
Fill in the blanks.
a) When we multiply 0.236 by 10, the digit moved from the
hundredths column to the tenths column.
b) When we multiply 0.236 by 10, the 6 digit moved from the
column to the column.
So when we multiply a number by 10, each digit moves one/two/three*
places to the left/right* in the place-value table. This makes a number
greater/smaller*.

How many tonnes of food would the elephant eat in 100 days? Study
the table to see what happens when we multiply a decimal number by
100.

UNIT 4 I Decimals