Question

Jennifer can clean her room in 2 hours, while John can clean the same room in 5 hours. How many hours would it take for them to clean the room together?

7
10
seven tenths
ten sevenths


I think the answer is tenth sevenths but im not sure! Please Help ASAP

Answer 1

Ten sevenths. Hope this helps

Answer 2

Answer: ten sevenths

Step-by-step explanation:

Given: Time taken by Jennifer to clean her room $t_1= 2 \text[ hours}$

Time taken by John to clean same room $t_2= 5\text[ hours}$

If they work together to clean the room , then the total time taken by them is given by :-

$\dfrac{1}{t}=\dfrac{1}{t_1}+\dfrac{1}{t_2}\\\\\Rightarrow\ \dfrac{1}{t}=\dfrac{1}{2}+\dfrac{1}{5}\\\\\Rightarrow\ \dfrac{1}{t}=\dfrac{5+2}{10}\\\\\Rightarrow\ \dfrac{1}{t}=\dfrac{7}{10}\\\\\Rightarrow\ t=\dfrac{10}{7}\text{ hours}$