Question

A and B can do a piece of work in 28 days and 35 days, respectively. They work on alternate days starting with A till the work gets completed. How long (in days) would it take A and B to complete the work?

• A. $$31\frac15$$
• B. $$31\frac12$$
• C. $$31$$
• D. $$31\frac19$$

Answer 1

Answer:

$$31$$

A can do the work in $=28$

B can do the work in $=35$

LCM of this two is the total work = 140

efficiency of A $= 140/28=5$

efficiency of B $= 140/35=4$

straiting A alternate with B the two day work is = 9

$140/9=15$and reminder 5

days $=15\times 2=30$

one day work is done by A

$30+1=31$