Page 72 - Math Smart - 7

O 5x + 1 = 7 Solution
5x + 1 = 7
5x + 1 -1 = 7 - Subtract 1 from both sides of the equation
1
5x = 6
Divide both sides of the equation by 5
/lhS = 5 X I +1
= 6 +
1
= 7

Investigate!

PAIR WORK
The mind reader game
The result obtained at the end of this game will tell you their age and
the month in which they were born.
Instructions
O Start with the number of the month In which you were born. (January is
1, February is 2, March is 3, etc).
@ Multiply this number by 4.
@ Add 10.

O Multiply by 25.
@ Add your age.
O Subtract 365 (the number of days in a year).
O Add 115. What is your final answer?

You should find that the last two digits of your answer are your age, and the
other digits represent your birth month.
Now try this on a friend to check if it works. Discuss the trick with them.
Questions
O Can you explain why it works using algebraic equation?
O Show your working clearly.

Check My

Understanding

O Solve these equations for x. Show your working clearly. Then check your answers by
substituting your answer into the equation to see if it is correct.
a) 2a: + 8 = 20 b) 5a: + 12 = 27 c) 4x - 3 = 9
d) 6x - 5 = 19 e) 0 = 4x - 15 f) 23 - 5x = 13
g) 100-7x = 44 h) f + 3 = 9 i) 7 - 12 = 18

A--3 6 +
A*
j) 9 + 2 = 10 k) = 15 I) 1 =

68 ( UNIT 3 I Introduction to Algebra and Equations