Question

6 persons can complete electronic fitting in a building in 7 days. How
many days will it take if 21 persons do the same job?​

Answer 1

$6 \: persons = 7days \\ 1person = \frac{7}{6} days \\ therefore.21 \: persons = \frac{7}{6} \times 21 \\ = \frac{49}{2} = 24.5 \\ thus \: it \: will \: take \: 24.5 \: days \: to \: do \: the \: same \: job....$

Answer 2

Answer:

2 days.

Step-by-Step Explanation:

→ 6 men can complete the electric fitting in a building in 7 days. So, $6 \ratio 7$

→ 21 men can do the job in $a$ days. So, $21 \ratio a$

We get,

$\therefore 6 \ratio 7 \ratio \ratio 21 \ratio a$

If the number of men will increase, So, the number of days for the job will decrease. Hence, here is inverse proportion.

Since in inversely proportional term, where x and y has two variations,

$\it x_1 x_2 = y_1 y_2 = k$

Where, k is a constant term.

Here,

x :- $x_1 = 6, \: x_2 = 7$

y :- $y_1 = 21, \: y_2 = a$

Therefore,

$\therefore \rm 6 \times 7 = 21 \times a$

$\implies \rm 42 = 21a$

$\implies \rm a = \frac{42}{21}$

$\implies \rm a = \cancel{\frac{42}{21}}$

$\implies \rm \bf a = 2$

Hence, 21 men can do that job in 2 days.