Page 41 - Math Smart - 7

o Spotlighir
O Write down the next four terms in each of the following sequences:
a) 8,6,4.2 , , b) 15,5,-5 , , The Dead Sea has a
c) 2, 3, 5, 8 , , d) -10, -6, -2, , , , depth of about 380 m.
e) 4, 3, 1. -2, -6 , , f) -10, -9. -l.-A , , The surface and shores of
the Dead Sea are about
O Three divers are diving in the Red Sea. 430 m below sea level.
Diver A is 20 m below sea level. This makes the Dead
Diver B is 13 m below sea level. Sea the lowest point on
Diver C remained on the boat at 1 metre above sea level. land and the deepest
a) How can we record their positions below the sea level? Write the hypersaline lake on
divers' positions using integers. Earth.
b) List the divers from highest position to lowest position.
@* Challenge! During winter, the temperature in Dudinka, a town in
Russia, can go as low as 40°C below zero. How would you record this
temperature as an integer? If the temperature drops by another 5°C,
what would the new temperature be?

Adding and subtracting integers Integers are also known

as directed numbers
In primary school, we learnt how to add and subtract positive numbers. In this because they have either
positive or negative sign.
section, we will learn how to add and subtract with negative numbers.
/Size of the
Addition with negative integers number
-3

Direction of
X
the number
Use the integer track that you have made earlier to work out: (-3) + 6.
Place your counter at -3 and move 6 units to the right.

" 1 1 1 I I I 1 To add a positive
-10 -9 -8 -7 -6 -5 -4 -3 -2 -1 0 1 2 3 4 5 6 7 8 9 10
integer, you move
Did you land on the number 3? to the right on a
So, -3 + 6 = 3. horizontal number line.