Answer:
3.73 hours
Step-by-step explanation:
In 1 hour, Lisa does 1/7th of the order while Bill does 1/8th of the order in an hour. To find out how long it will take them to fill the order, we have to:
Step 1:
Add the rate of both Lisa and Bill together
1/7 + 1/8
Step 2:
Since both denominators of the fractions are different, you have to find the least common multiple of 7 and 8
7·8= 56 8·7= 56
which is 56.
Step 3:
Then, you have to multiply the numerator of 1/7 with 8 and the numerator of 1/8 with 7.
1·8= 8 1·7= 7
The fractions would now have equal denominators:
Lisa: 8/56 Bill: 7/56
Step 4:
Now, you can add them together
8/56 + 7/56
which equals to 15/56. Both Lisa and Bill together completes 15/56th of the order in 1 hour.
Step 5:
15/56 is not the final answer as it is the RATE of them working together. To find how long it will take them total to complete the order, you must divide 56 with 15.
56/15
which is 3.73 hours in decimal form (rounded).