Use of Unknowns

 1.8 Using Unknown

We will learn to determine the value of one for a mathematical sentence.

• The unknown is represented by letters.

Unknown can be in three positions in a mathematical sentence:
i. a × 23 = 46
ii. 114 × b = 342
iii. 20 × 3 = c

EXAMPLE OF USAGE OF UNKNOWNS IN ADDITION OPERATIONS

$$2\,183+Q=62\,985$$

Step 1 :

\begin{aligned} 2\,183+Q&=62\,985 \\Q&=62\,985-2\,183 \end{aligned}

Step 2 :

$$\begin{array}{rr} 6\space2\,\space\space9\space8\space5 \\-\quad\quad2\,\space\space1\space8\space3 \\\hline6\space0\,\space\space8\space0\space2 \\\hline \end{array}$$

EXAMPLE OF USAGE OF UNKNOWNS IN SUBTRACTION OPERATIONS

$$P-24\,396=63\,014$$

Step 1 :

\begin{aligned} P-24\,396&=63\,014 \\P&=63\,014+24\,396 \end{aligned}

Step 2 :

$$\begin{array}{rr} \small{\color{red}{1}}\space\,\small{\color{green}{1}}\space\space\space\, \\6\space3\,\space\space0\space1\space4 \\+\quad2\space4\,\space\space3\space9\space6 \\\hline8\space7\,\space\space4\space1\space0 \\\hline \end{array}$$