Page 43 - Math Smart - 7

jflkj Amazing
IWIathom:
Mathematician
What about -4 + (-5)?
The Chinese number
rod system of 200 BCE
represented positive
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10 numbers in red and
negative numbers in
black to work with
We start from (-4) and move 5 units to the left. So, -4 + (-5) = -9.
transactions. But it was
We can also use number discs to help us. only in the 7'" century
that negative numbers
were dealt with by the
0© ©0 Indian mathematician
Brahmagupta (598).
©0 Brahmagupta established
the basic mathematical
© rules for dealing with zero:
(1+0 = 1; 1 - 0 = 1; and
1x0 = 0).
Check My
Understanding 1
+
CO
Let's practise adding positive and negative integers.
O Work out the values.
a) (-3) + (-20) b)
c) (-5) + (-6) d) (-3) + (-8)
e) (+5)+ (-12) f) (-6) + (-3)

g) (-10)+ (+18) h) (+15)+ (-3)
i) ^ + (-1) j) -8 + (-5)
k) -7 +(-2) 1) -14 + (-^)
m)-4 + (-7) + 3 n) 4 + 2 + (-3) + (-1)
o) -4 + (+5) + 1 P) ^ 3 + (-2) +
+
6
q) (-18) + (-2) r) -4+ (-17)
s) (-14)+ (14) t) 12+ (-12)

e A submarine is 111 m below sea level. It rises by 7 m every minute. What
is the depth of the submarine after 10 minutes?
o The temperature went up from -5°C to Find the difference between
the temperatures.
o Bangkok is a city that is 150 cm below sea level. Another city, Kolkata,
is 914 cm above sea level. Represent the altitudes of the cities using
integers. Then, find the difference between the cities.

Q