Respuesta :
The epson stylus 850 can print Helen's project in 12 mins
TThe epson stylus 500 can print that same project in 42 minutes
Work = rate x time
the two printers are working on the same assignment
therefore, we will be adding their rate
for epson 850
work = rate x time
work= 1
time = 12mins
1 = rate x 12
make rate the subject of the formula by dividing bott sides by 12
1 / 12 = rate x 12 / 12
rate = 1/ 12
for epson 500
work = rate x time
time = 42 mins
work = 1
applying the same process
1 = rate x 42
rate = 1/42
since they are both working together
Total rate = 1 /12 + 1/42
lcm is 84
since 12 and 42 are factors of 84
Total rate = 1/12 + 1/42
total rate = 84 * 1 /12 + 84*1 / 42 /84
total rate = 7 + 2 / 84
total rate = 9/84
to calculate the time they worked together
work = rate x time
1 = 9/84 x time
make time the subject of the formula
1 / 9/84 = time
time = 84/9
time = 28 / 3
Time = 9 1/3 min
Option B
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