A is able to complete a task in 15 days, while B takes 20 days to finish the same task. If they collaborate and work together for 4 days, what fraction of the work will still remain?

A is able to complete a task in 15 days, while B takes 20 days to finish the same task. If they collaborate and work together for 4 days, what fraction of the work will still remain?

A किसी कार्य को 15 दिनों में पूरा कर सकता है, जबकि B उसी कार्य को 20 दिनों में पूरा करता है। यदि दोनों मिलकर 4 दिन कार्य करें, तो कार्य का कितना भाग शेष रहेगा?

Options / विकल्प

A. $\frac{1}{4}$

B. $\frac{7}{15}$

C. $\frac{8}{15}$ ✅

D. $\frac{11}{15}$

Answer / उत्तर

✅ $\frac{8}{15}$

Solution / समाधान

Method 1: Using Work Rates

विधि 1: कार्य-दर का उपयोग

A's one-day work:

B's one-day work:

Together, one-day work:

Work done in 4 days:

Remaining work:

Shortcut Trick / शॉर्टकट ट्रिक

Take total work as:

A's efficiency:

B's efficiency:

Combined efficiency:

Work done in 4 days:

Remaining work:

Fraction remaining:

Final Answer / अंतिम उत्तर

✅ Correct Answer / सही उत्तर: $\frac{8}{15}$

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