Bobby had a party while his parents were away for the weekend. Bobby estimated that if his 9 friends help him to clean the house, they will be able to finish cleaning in 8 hours before his parents return. After two hours of cleaning, Bobby's parents call and say they are just two hours from home. How many more friends does Bobby need to call for help to finish cleaning in time?

Using an inverse rule of three, it is found that Bobby needs to call 18 more people.

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The rule of three is:

9 people - 6 hours

x people - 2 hours.

Multiplying by line:

Already has 9 people, in total needs 97, so he needs to call 27 - 9 = 18 more people.

A similar problem is given at link

Here, we are required to determine how many more friends does Bobby need to call for help to finish cleaning in time.

Bobby needs 18 more friends to help finish the cleaning in time.

The question above can be solved by ratios and proportions: As such;

Since 9 friends can finish in 8 hours;

After 2 hours, they must have completed 25 % (i.e 1 quarter of the job).

As such, the 9 friends now need 6 hours to complete the rest of the cleaning.

However, since the parents are now 2 hours from home;

Let the number of friends Bobby needs to complete the job in 2 hours be x.

Since;

9 friends take 6hours to complete the cleaning,

then, In 2 hours, Bobby needs, x = (9×6)/2 friends to complete the job.

Ultimately, Bobby needs 27 friends to complete the cleaning in 2 hours.

However, since Bobby has 9 friends on the cleaning already, he needs (27 - 9) = 18 friends more to complete the cleaning in 2 hours.

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x =±sqrt(1/3)

step-by-step explanation:

x+4/6x=1/x

multiply each side by 6x to get rid of the fractions

6x*(x+4/6x)=1/x*6x

distribute

6x^2 +4 = 6

subtract 4 from each side

6x^2 +4-4 = 6-4

6x^2 =2

divide by 6

6x^2/6 = 2/6

x^2 = 1/3

take the square root of each side

sqrt(x^2) = ±sqrt(1/3)

x =±sqrt(1/3)