Question

7. Pippin and Sam are painting a fence. Sam could paint the whole fence alone in 12
hours. Pippin could paint the whole fence alone in 8 hours. Sam starts painting at 1
p.m. and Pippin joins him at 3p.m. What time do they finish?​

Answer 1

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GiveN:

• Sam can paint alone in like 12 hours.
• Pipim can paint in 8 hours.
• Sam starts painting at 1 pm and Pipin joins him at 3 pm.

To FinD:

• When they will finish?

Step-wise-Step Explanation:

Sam started alone at 1 pm and Pipin joined him 3 pm. So, he worked alone for 2 hours.

• Time taken by Sam

= 12 hours

• Sam's 1 hour work

= 1/12th of the work.

• He works for 2 hours

= 1/12 × 2

= 1/6th of the work.

Remaining work

= 1 - 1/6 = 5/6th work.

━━━━━━━━━━━━━━━━━━━━

At 3 pm, they started together.

• Sam's 1 hour work = 1/12

• Pippin's 1 hour work = 1/8

• Then, Sam and Pipin's 1 hour work

= 1/12 + 1/8

= 5/24

• Then total time taken to complete 1 work

= 24/5 hrs

• Then, for remaining 5/6th of the work:

= 5/6 × 24/5 hours

= 4 hours.

They will complete after 4 hours i.e. 7 pm

And we are done! :D

Answer 2

At 7 pm they will finish their work.

Please refer to above image for full solution.