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📈 Chapter 13: Two Variables, One Line • Exercise Set 13.1

Verified step-by-step solutions for your class notes.

Q1

Write a linear equation in two variables in which $a = 3$, $b = 0$ and $c = -\frac{1}{5}$.

Answer: The standard form is $ax + by + c = 0$.
Substituting the given values: $3x + 0y - \frac{1}{5} = 0$.
This can also be written simply as $3x - \frac{1}{5} = 0$, or multiplied by 5 to remove the fraction: $15x - 1 = 0$.

Q2

Complete the following table after expressing the given linear equations in standard form.

Linear equation in two variablesStandard FormCoefficient of xCoefficient of yConstant term
$y - 15 = \sqrt{2}x$
$3y - 2x = 0$
$5x = 3y$
$x = 8$
$3y = 1$
Linear equationStandard Form ($ax+by+c=0$)Coefficient of x ($a$)Coefficient of y ($b$)Constant term ($c$)
$y - 15 = \sqrt{2}x$$-\sqrt{2}x + y - 15 = 0$ (or $\sqrt{2}x - y + 15 = 0$)$-\sqrt{2}$ (or $\sqrt{2}$)$1$ (or $-1$)$-15$ (or $15$)
$3y - 2x = 0$$-2x + 3y + 0 = 0$$-2$$3$$0$
$5x = 3y$$5x - 3y + 0 = 0$$5$$-3$$0$
$x = 8$$1x + 0y - 8 = 0$$1$$0$$-8$
$3y = 1$$0x + 3y - 1 = 0$$0$$3$$-1$
Q3


(i) The cost of a notebook is twice the cost of a pen. Consider the cost of a notebook to be ₹t and that of a pen to be ₹p. Charlie wrote $t = 2p$ whereas Meera wrote $p = 2t$. Which of these two representations is correct?
(ii) In a one-day International Cricket match... two Indian batsmen together scored 176 runs. Manisha expressed this situation as $x + y = 176$, where the number of runs scored by one batsman is x, and the number of runs scored by the other is y. Is this a correct representation?

Answer:
(i) Charlie's representation, $t = 2p$, is correct. Since the notebook ($t$) is twice as expensive as the pen ($p$), you must multiply the cost of the pen by 2 to equal the cost of the notebook.
(ii) Yes, this is a correct representation. The sum of the runs scored by the first batsman ($x$) and the second batsman ($y$) equals the total runs they scored together (176).