Page 98 - Math Smart - 7

Pi (ji) is a special number
3.141592653589793238462
that is used in calculations
involving circles. It is obtained 6433832795028841971693
by dividing the circumference
9937510582097494459230
of a circle by its diameter. The
7816406286208998628034
answer is a decimal. Pi is a
decimal with a never ending 8253421170679821480865
number of decimal places.
To simplify working with
the value of pi, it is usually
rounded off to two decimal
places and written as 3.14. s Figure 4.1 Pi has a never ending number of
decimal places.

0i Investigate!

Look at the number line. Can you see a pattern? When do we round up to
the bigger whole number? When do we round down to the smaller whole
number?

O Fill in the missing numbers. The first one has been done for you.
19
a) 19.1 is rounded to | b) 19.2 Is rounded to
c) 19.3 is rounded to | d) 19.4 is rounded to

e) 19.5 is rounded to | f) 19.6 Is rounded to

g) 19.7 is rounded to h) 19.8 Is rounded to

i) 19.9 is rounded to
0 Use your answers In Question 1 to write down some conclusions about

rounding decimals to the nearest whole number.
a) When the digit in the tenths column is 1, 2, 3 or 4, then the number
is rounded to the whole number .
b) When the digit in the tenths column Is 5, 6, 7, 8 or 9, then the
number Is rounded to the whole number .

19 19.1 19.2 19.3 19.4 19.5 19.6 19.7 19.8 19.9 20

When we a number to the nearest whole number, we look
at the digit in the place.
If the digit < 5, we round It to the _ whole number,
If the digit = 5, we round It to the _ whole number,
If the digit > 5, we round It to the _ whole number.

UNIT 4 I Decimals