Question

Observe the following tables and find if X and Y are directly proportional
(i)

x	20	17	14	11	8	5	2
y	40	34	28	22	16	10	4

(ii)

x	6	10	14	18	22	26	30
y	4	8	12	16	20	24	28

(iii)

x	5	8	12	15	18	20
y	15	24	36	45	54	60

Answer 1

$\left(i\right)\frac{20}{40}=\frac{17}{34}=\frac{14}{28}=\frac{11}{22}=\frac{8}{16}=\frac{5}{10}=\frac{2}{4}=\frac{1}{2}$

Hence, $x$ and $y$ are directly proportional.

$\left(ii\right)\frac{6}{4}\ne \frac{10}{8}\ne \frac{14}{12}\ne \frac{18}{16}\ne \frac{22}{20}\ne \frac{26}{24}\ne \frac{30}{28}$

Hence, $x$ and $y$ are not directly proportional.

$\left(iii\right)\frac{5}{15}=\frac{8}{24}=\frac{12}{36}=\frac{15}{45}=\frac{18}{54}=\frac{20}{60}=\frac{1}{3}$

Hence, $x$ and $y$ are directly proportional.