Question

A company orders a number of bottles from a factory.

The 8 machines in the factory could make all the bottles uv 5 days. All the machines work at the same rate.
For 2 days, only 4 machines are used to make the bottles. From the 3rd day, all 8 machines are used to make the bottles.
Work out the total number of days taken to make all the bottles.

Answer 1

if 8 machine can do it in 5 days then 40 machines can do it in 1 day (8x5=40 machines worth of work)
for the first 2 days you have 4 machines only (2x4=8 machines worth of work)
leaving (40-8) 32 machines worth of work. From day 3 you have all 8 machines working. 32/8 = 4 more days
2 days (4 machines) and another 4 days (with 8 machines) = 6days to make all the bottles