A alone can do a piece of work in 6 days and B alone in 8 days. A and B undertook to do it for 3200 TK. With the help of C, they completed the work in 3 days.How much is to be paid to C ?
Solution
Correct Answer: Option B
A alone can do the work in 6 days.
So, in 1 day A does $\frac{1}{6}$ part of the work.
B alone can do the work in 8 days.
So, in 1 day B does $\frac{1}{8}$ part of the work.
With the help of C, the work is completed in 3 days.
So, in 1 day (A + B + C) do $\frac{1}{3}$ part of the work.
Therefore, in 1 day C alone does:
= $\frac{1}{3}$ - $(\frac{1}{6} + \frac{1}{8})$ part
= $\frac{1}{3}$ - $(\frac{4 + 3}{24})$ part
= $\frac{1}{3}$ - $\frac{7}{24}$ part
= $\frac{8 - 7}{24}$ part
= $\frac{1}{24}$ part
The ratio of daily work of A, B and C:
A : B : C = $\frac{1}{6}$ : $\frac{1}{8}$ : $\frac{1}{24}$
= $(\frac{1}{6} \times 24)$ : $(\frac{1}{8} \times 24)$ : $(\frac{1}{24} \times 24)$
= 4 : 3 : 1
Total Amount = 3200 Tk
Sum of the ratios = 4 + 3 + 1 = 8
So, C will be paid:
= 3200 $\times \frac{1}{8}$ Tk
= 400 Tk.
উত্তর: 400 Tk
### কুইক সমাধান (Short Method):
3 দিনে A এবং B মোট কাজের কতটুকু সম্পন্ন করে তা বের করে মোট কাজ (1 অংশ) থেকে বিয়োগ করলে C এর কাজের পরিমাণ পাওয়া যাবে। কারণ, প্রত্যেকে কাজের যতটুকু অংশ সম্পন্ন করবে, পারিশ্রমিক ঠিক ততটুকু অংশই পাবে।
A's 3 days work = $3 \times \frac{1}{6} = \frac{1}{2}$ part
B's 3 days work = $3 \times \frac{1}{8} = \frac{3}{8}$ part
So, C's work = Total work - (A's work + B's work)
= $1 - (\frac{1}{2} + \frac{3}{8})$
= $1 - \frac{4 + 3}{8}$
= $1 - \frac{7}{8}$
= $\frac{1}{8}$ part
$\therefore$ C's share = $3200 \times \frac{1}{8}$ = 400 Tk.