1.

A, B, C can finish a work in 8 hours, 9 hours and 12 hours respectively. They all started working together, but A left 3 hours before completion, B left 4 hours before completion and C continued the work till end. The work is finished in:1). 5.3 hours2). 5.7 hours3). 6.8 hours4). 7.1 hours

Answer»

A’s 1 hour work = 1/8

B’s1 hour work = 1/9

C’s 1 hour work = 1/12

Let the work is completed in ‘x’ hours.

A worked for (x – 3) hours.

B worked for (x – 4) hours.

C worked for x hours.

Thus, we have,

(x – 3)/8 + (x – 4)/9 + x/12 = 1

⇒ 9(x – 3) + 8(x – 4) + 6X = 72

⇒ 9x – 27 + 8X – 32 + 6x = 72

⇒ 23x = 131

∴ x = 131/23 = 5.7 hours.


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