# Aptitude - Time and Work - Discussion

Discussion Forum : Time and Work - General Questions (Q.No. 1)

1.

A can do a work in 15 days and B in 20 days. If they work on it together for 4 days, then the fraction of the work that is left is :

Answer: Option

Explanation:

A's 1 day's work = | 1 | ; |

15 |

B's 1 day's work = | 1 | ; |

20 |

(A + B)'s 1 day's work = | 1 | + | 1 | = | 7 | . | ||

15 | 20 | 60 |

(A + B)'s 4 day's work = | 7 | x 4 | = | 7 | . | ||

60 | 15 |

Therefore, Remaining work = | 1 - | 7 | = | 8 | . | ||

15 | 15 |

Discussion:

320 comments Page 1 of 32.
Lakshmanan S said:
3 months ago

How come remaining work 1- 7/15? Please explain me.

(46)

Sahil said:
3 months ago

4( 1/15 + 1/20 ) = work done by both of them together

Work Done + Work left =1 =>because the work is 100% completed

4( 1/15 + 1/20 ) + work left = 1;

work left = 1 - (28/ 60);

Then, work left = 8/15;

Work Done + Work left =1 =>because the work is 100% completed

4( 1/15 + 1/20 ) + work left = 1;

work left = 1 - (28/ 60);

Then, work left = 8/15;

(24)

Portia said:
3 months ago

How did 1/15 +1/20 turn into 7/60? Someone, please explain.

(24)

NADIPUDI SIRISHA said:
4 months ago

Thank you for explaining the answer @Giri.

(16)

Durga prasad said:
5 months ago

Lcm of 15 and 30 = 60 units.

A's per day work = 60/15 = 4units.

B's per day work = 60/20 = 3units.

A+B's per day work = 4 + 3 = 7units.

A and B together do the work in 4 days.

= 4 * 7 = 28units.

Remaining work = 32/60 = 8/15.

A's per day work = 60/15 = 4units.

B's per day work = 60/20 = 3units.

A+B's per day work = 4 + 3 = 7units.

A and B together do the work in 4 days.

= 4 * 7 = 28units.

Remaining work = 32/60 = 8/15.

(116)

Giri said:
5 months ago

Just take LCM on 15 and 20 of 60.

Total work 60.

Capacity A 4 and capacity B 3 total 7.

They both worked together for 4 days and completed work 28.

Remaining work 32/60,

So, the Answer 8/15.

Total work 60.

Capacity A 4 and capacity B 3 total 7.

They both worked together for 4 days and completed work 28.

Remaining work 32/60,

So, the Answer 8/15.

(39)

Mish said:
6 months ago

@All.

Why (A+B)'s 4 days of work is calculated?

Why it's not 3,5,6,7 or any other day?

What is the logic behind it?

Why (A+B)'s 4 days of work is calculated?

Why it's not 3,5,6,7 or any other day?

What is the logic behind it?

(9)

Zak said:
7 months ago

How come 7/60? Please explain.

(26)

Dinesh kumar said:
8 months ago

A = 1/15

B = 1/20

(A+B) = 1/15+1/20 = 7/15

The remaining work = 1-7/15 = 8/15.

B = 1/20

(A+B) = 1/15+1/20 = 7/15

The remaining work = 1-7/15 = 8/15.

(25)

Jeevanantham M said:
10 months ago

@Ayansh.

For this;

(A+B) 's work rate = 1/15 + 1/20 = (4/60 + 3/60) = 7/60.

For this;

(A+B) 's work rate = 1/15 + 1/20 = (4/60 + 3/60) = 7/60.

(19)

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