Question

Ignore swell and shrinkage for this problem.

Answer 1

Answer:

(a) 5.3

(b) 6

(c) 5

Explanation:

First we calculate time required for excavator to fill 1 truck:

Time to Fill 1 Truck = (No. of Cycles To Fill)(Cycle Time)

Time to Fill 1 Truck = (3)(33 sec)

Time to Fill 1 Truck = 99 sec

Now, we find the time taken by a truck to come back to excavator, after dumping:

Time of Return = Hauling Time + Time to Dump + Time to Come Back

Time of Return = 5 min + 45 sec + 3 min

Time of Return = 300 sec + 45 sec + 180 sec

Time of Return = 525 sec

(a)

In order to balance the output of excavator with number of trucks, following condition must be satisfied:

Time of Return = (No. of Trucks)(Time to Fill 1 Truck)

525 sec = (No. of Trucks)(99 sec)

No. of Trucks = 525 sec/99 sec

No. of Trucks = 5.3

(b)

If we round up the number of trucks, we get:

No. of Trucks = 6

(c)

If we round down the number of trucks, we get:

No. of Trucks = 5