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Mathematics

A and B together can do a piece of work in 6 days. If A’s one day’s work is 1121\dfrac{1}{2} times the one day's work of B, find how many days, each alone can finish the work.

Linear Equations

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Answer

Let A's one day work be x and B's one day work be y.

According to first condition given in the problem,

A works 1121\dfrac{1}{2} times of B,

x=112y\Rightarrow x = 1\dfrac{1}{2}y

x=32y\Rightarrow x = \dfrac{3}{2}y

⇒ 2x = 3y

⇒ 2x - 3y = 0     ……(1)

Also given, A and B together can do a piece of work in 6 days.

x+y=16\therefore x + y = \dfrac{1}{6}

⇒ 6(x + y) = 1

⇒ 6x + 6y = 1     …(2)

Multiplying (1) by 2 we get,

⇒ 2(2x - 3y) = 2 × 0

⇒ 4x - 6y = 0     …(3)

Adding equations (2) and (3) we get,

⇒ 6x + 6y + 4x - 6y = 1 + 0

⇒ 10x = 1

⇒ x = 110\dfrac{1}{10}

Substituting value of x in equation (1), we get :

⇒ 2 × 110\dfrac{1}{10} - 3y = 0

15\dfrac{1}{5} - 3y = 0

⇒ 3y = 15\dfrac{1}{5}

⇒ y = 115\dfrac{1}{15}

Since, A's one day work is x and B's one day work is y, so A can do complete work in 1x\dfrac{1}{x} and B can do work in 1y\dfrac{1}{y} days.

1x=1110\dfrac{1}{x} = \dfrac{1}{\dfrac{1}{10}} = 10 days

1y=1115\dfrac{1}{y} = \dfrac{1}{\dfrac{1}{15}} = 15 days

Hence, A can finish the work in 10 days while B can finish the work in 15 days.

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