Time And Work All Competence Aptitude
Question 121
A and B were assigned to do a job for an amount of 1,200. A alone can do it in 15 days, while B can do it in 12 days. With the help of C, they can finish in 5 days. The share of amount that C earns is ?
Let's first find the rates at which A, B, and C work.
A can complete the job in 15 days, so his rate of work is \( \dfrac{1}{15} \) of the job per day.
B can complete the job in 12 days, so his rate of work is \( \dfrac{1}{12} \) of the job per day.
Together, A, B, and C can complete the job in 5 days, so their combined rate of work is \( \dfrac{1}{5} \) of the job per day.
Let the rate of work of C be \(C\).
Now, since A, B, and C work together, their combined rate of work is the sum of their individual rates of work:
\[ \dfrac{1}{15} + \dfrac{1}{12} + C = \dfrac{1}{5} \]
Now, let's solve for \(C\):
\[ \dfrac{1}{15} + \dfrac{1}{12} + C = \dfrac{1}{5} \]\[ \dfrac{4}{60} + \dfrac{5}{60} + C = \dfrac{12}{60} \]\[ \dfrac{9}{60} + C = \dfrac{12}{60} \]\[ C = \dfrac{12}{60} - \dfrac{9}{60} \]\[ C = \dfrac{3}{60} \]\[ C = \dfrac{1}{20} \]
So, the rate of work of C is \( \dfrac{1}{20} \) of the job per day.
Now, let's find the amount that C earns. Since C works for 5 days, the amount C earns is proportional to the fraction of the work C completes:
\[ \text{Amount earned by C} = \dfrac{\text{Fraction of work completed by C}}{\text{Total fraction of work}} \times \$1200 \]
The fraction of work completed by C in 5 days is \(5 \times \dfrac{1}{20} = \dfrac{1}{4}\). The total fraction of work completed by A, B, and C in 5 days is 1.
So,
\[ \text{Amount earned by C} = \dfrac{\dfrac{1}{4}}{1} \times \$1200 \]\[ \text{Amount earned by C} = \dfrac{1}{4} \times \$1200 \]\[ \text{Amount earned by C} = \$300 \]
Therefore, the share of the amount that C earns is \$300.
Not clear enough?
Question 122
Twenty women together can complete a work in 16 days. 16 men together can complete the same work in 15 days. The ratio of the working capacity of a man to that of a woman is ?
First, let's find the work rate of one woman and one man.
Let \( W \) be the work rate of one woman, and \( M \) be the work rate of one man.
Given that 20 women together can complete the work in 16 days, we can find the work rate of one woman:
\[ \text{Work rate of one woman} = \dfrac{1}{20 \times 16} \]
Similarly, given that 16 men together can complete the work in 15 days, we can find the work rate of one man:
\[ \text{Work rate of one man} = \dfrac{1}{16 \times 15} \]
Now, let's calculate these values:
\[ \text{Work rate of one woman} = \dfrac{1}{320} \]\[ \text{Work rate of one man} = \dfrac{1}{240} \]
Now, we can find the ratio of the work rate of a man to that of a woman:
\[ \dfrac{\text{Work rate of one man}}{\text{Work rate of one woman}} = \dfrac{\dfrac{1}{240}}{\dfrac{1}{320}} \]\[ \dfrac{\text{Work rate of one man}}{\text{Work rate of one woman}} = \dfrac{320}{240} \]\[ \dfrac{\text{Work rate of one man}}{\text{Work rate of one woman}} = \dfrac{4}{3} \]
So, the ratio of the working capacity of a man to that of a woman is \(4:3\).
Therefore, the correct answer is \(4:3\).
Not clear enough?
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