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3 Smart
Smart
Given that x = 3 and y = 2, find the value of 8x – 5y + 7.
A scientific calculator can
be used to determine the
8x – 5y + 7 = 8(3) – 5(2) + 7 value of an expression.
For instance, in Example 3:
= 24 – 10 + 7 1. Press
= 21 8 ALPHA X – 5
ALPHA Y + 7 CALC
4 Screen displayed
X?
1
In a class, of the boys are members of Kadet Remaja
3 2. Enter the given value
Sekolah whereas 9 girls are not members of Kadet Remaja of x. CHAPTER
Sekolah. Press 3 =
(a) Write an expression for the total number of members of Screen displayed 5
Kadet Remaja Sekolah in the class. Y?
(b) If there are 12 boys and 16 girls in the class, calculate 3. Enter the given value
the total number of members of Kadet Remaja Sekolah of y.
in the class. Press 2 =
Screen displayed
8X – 5Y + 7
(a) Let the number of boys = x 21
and the number of girls = y
1
Thus, the total number of members of Kadet Remaja Sekolah = x + y – 9
3
(b) When x = 12 and y = 16,
1
the total number of members of Kadet Remaja Sekolah = (12) + 16 – 9
3
= 4 + 16 – 9
= 11
Self Practice 5.1c

1. Given that p = 5, q = 2 and r = – 4, find the value for each of the following expressions:
r
(a) 2p + q (b) 3q – 4r + 8 (c) 5(p – r) (d) + 7q – 3
2
2. Encik Adnan and Mr Tan donate rice to the flood victims. Encik Adnan donates 8
bags of rice and each bag has a mass of x kg. Mr Tan donates 4 bags of rice and each
bag has a mass of y kg.
(a) Write an expression for the total mass of rice donated by them.
(b) If x = 5 and y = 10, calculate the total mass of rice donated by them.
3. Jane and Kamalesh buy m and n Hari Raya greeting cards respectively at a price of
RMp for each card. These cards will be given to their Muslim friends.
(a) Write an expression for the difference in the amount of money that they had paid.
(b) If m = 8, n = 6 and p = 1.5, calculate the difference in the amount of money they
had paid.

109
Algebraic Expressions

05 TB Math F1.indd 109 11/10/16 12:13 PM