It takes emily eight hours to paint her house. mike can paint the same area in nine hours. find how long it would take them if they worked together.

7.58 hours

15.34 hours

3.56 hours

4.24 hours

It would take them 4.24 hours if they worked together.

Explanation:

We are given that

time taken by emily to paint her house = 8 hours and

time take by Mike to paint the same area = 9 hours

We have to find the time taken by them if the work together, let this be x so x will be given by,  

= 4.24 hours

which is the time taken by Emily and Mike to paint the house when they do it together.

the largest number of the four options is 1.8 x 10-2

you have it in scientific notation.

1.80 x 10-6   = 0.00000180

1.80 x 10-4   = 0.000180 (bigger, or "less small", than the former one)

so

1.8 x 10-2       = 0.0180. as you see. the "less small", or the biggest one of them all.

as you have negative exponent, it means you are dividing 1.8 by 100 (i.e. moving the dot towards left, two times).

if you had positive exponent for the scientific notation, power of tenths, you would be multiplying times 100 (moving the dot towards right) as below:

1.8 x (10)2 = 180

so. if you have negative exponent in scientific notation, move the dot toward left. if it is positive, toward right as many times the exponent tells you.