Problema Solution
Roger is writing a final exam for his chem. 101 class. he knows it will take him 10 hrs. to finish writing the exam if he works by hiimself. his colleague, william, can write the same exam in 7 hrs. by himself. how long will it take them to write the exam if they both work together?
Answer provided by our tutors
Rogers rate is 1/10 exams per hour
Williams rate is 1/7 exams per hour
If together new need x hours to write the exam then their together rate is 1/x exams per hour and we have
1/10 + 1/7 = 1/x
by solving we find
x = 70/17 hr
x = 4 hr 7 min
click here to see the step by step solution of the equation
Together Roger and William can write the exam in 4 hours and 7 minutes.