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## JSS1: MATHEMATICS - 2ND TERM

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Lesson 1, Topic 2
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# Using Letters to Represent Numbers

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In Mathematics, we use letters of the alphabet to stand for numbers instead of boxes.

We write 10 Â  + Â  x Â  instead of 10 Â  + $$\scriptsize \boxed{?}$$. We can use any letter.

### Example:

Each sentence is true. Find the number that each letter stands for.

i. $$\scriptsize x = 2 + 7 \\ \rightarrow \scriptsize x = 9$$

ii. $$\scriptsize y = 14\: – \: 4 \\ \rightarrow \scriptsize y = 10$$

iii. $$\scriptsize 12 + 8 = P \\ \rightarrow \scriptsize P = 20$$

iv. $$\scriptsize 2 + m = 5 \\ \rightarrow \scriptsize m = 5 \: – \: 2 \\ \rightarrow \scriptsize m = 3$$

v. $$\scriptsize C + 11 = 30 \\ \rightarrow \scriptsize C = 30 \: – \: 11 \\ \rightarrow \scriptsize C = 19$$

vi. $$\scriptsize P \: \times \: 3 = 18 \\ \rightarrow \scriptsize P = \normalsize \frac{18}{3} \\ \rightarrow \scriptsize P = 6$$

vii. $$\scriptsize 8 \: \times\: x = 24 \\ \rightarrow \scriptsize x = \normalsize \frac{24}{8} \\ \rightarrow \scriptsize x = 3$$

viii. $$\scriptsize x \: \div \: 7 = 2 \\ \rightarrow \scriptsize 14 \: \div \: 7 = 2 \\ \scriptsize \therefore x = 14$$

or

$$\scriptsize x \: \div \: 7 = 2 \\ \rightarrow \frac{x}{7} \scriptsize = 2\\ \scriptsize x = 2 \: \times \: 7 \\ \scriptsize \therefore x = 14$$

ix. $$\scriptsize 10 \: \div \: f = 2 \\ \rightarrow \scriptsize 10 \: \div \: 5 = 2 \\ \rightarrow \scriptsize f = 5$$

or

$$\scriptsize 10 \: \div \: f = 2 \\ \rightarrow \frac{10}{f} = 2\\ \rightarrow \scriptsize 10 = 2 \: \times \: f \\ \rightarrow \scriptsize f = \normalsize \frac{10}{2} \\ \rightarrow \scriptsize f = 5$$

x. $$\scriptsize 36 = x + x + x \\ \rightarrow \scriptsize 36 = 3x \\ \rightarrow \scriptsize x = \normalsize \frac{36}{3} \\ \rightarrow \scriptsize x = 12$$