My son has a problem with his math HW, he asked me and his mother but we dont know. Please help me to help him

Question

Shaquille can deliver newspapers in 30 minutes. It takes Kobe 20 minutes to do the same route. How long would it take them to deliver the newspapers if they work together?


Define a variable and write an equation that represents the problem. Do not solve. (Note: Rate x Time = Work done)


Please show me some work so I can actually explain it to him, instead of giving him the answer without him understanding. I want him to understand the concept. THANK YOU SOOO MUCH. REMEMBER--BEST ANSWER GETS 10 WHOLE POINTS!!!!!!!!

We live in Washington so if anyone goes to DC High School, you know my son.

Answer 1

I remember these. The rate of S is 1/30. In 30min he can do 1unit of work. The rate of K is 1/20; it takes 20min to do 1 unit of work (example: rate*time = 1 unit work, 1/20 * 20 = 1)

So, how long working together to do 1 unit of work? Remember, the time, t, is the same for both.

t/30 + t/20 = 1
Cross multiply: 20t/600 + 30t/600 = 600
t = 12min
As an aside, if they both worked at a rate of 1/30 then it would take half the time if they worked together, or 15min

Answer 2

Le n be the total number of newspapers to be delivered
then Shaquille delivers 1 newspapers every 30/n minutes
Kobe can deliver 1 in 20/n minutes
or
Shaquill can do 2 papers in 60/n minutes, and
Kobe can do 3 in 60/n minutes
so
togehter they can do 5 in 60/n minutes
to do n papers together, they need using proportions

*** do not look below for answers ****











60/n x n/5 = 12 minutes

Answer 3

lets say the time Shaquille can deliver the papers is 1/3 hours (20 minutes = 1/3 of an hour) and Kobe 1/2 of an hour (30 minutes = 1/2 of an hour)

let w be the work time of each.

Shaquille: w/1/3 Kobe: w/1/2

w/1/3 + w/1/2 = w/t (let t be the time)

we put w as 1 now

1/(1/3) + 1/(1/2) = 1/t

3 + 2 = 1/t

5 = 1/t

therefore t = 1/5

1/5 of an hour = 25 minutes

So it takes Shaquille and Kobe 25 minutes to deliver the newspaper together.

Answer 4

Simplest approach:
Write down how much of the work each person can do in
1 minute.
It takes Shaquille 30 minutes to do his whole job.
So in 1 minute he can do 1/30 of it.
Similarly Kobe can do 1/20 of the work in 1 minute.
Suppose it takes them x minutes to do the job
when working together. Then in 1 minute they can do
1/x of the work.
So 1/30 + 1/20 = 1/x. There's your equation.
Now solve it:
50/600 = 1/x
x = 600/50 = 12.
Together they can do the job in 12 minutes.

Answer 5

Hopefully, the following should be easy to follow:

Let the work (delivering all newspapers) be: w
Let Shaq's rate of work be: r1
Let Kobe's rate of work be: r2

Since: rate * time = work

Shaq's rate is:
r1 * (30min) = w
r1 = w / 30

Kobe's rate is:
r2 * (20min) = w
r2 = w / 20

When they work together, they both work at the same time...

So before, with Shaq alone (30 min to finish):
r1 * 30 = w

And with Kobe alone (20 min to finish):
r2 * 20 = w

Now, working together (T min to finish, same amount of work):
r1*T + r2*T = w
T *(r1 + r2) = w
T * (w/30 + w/20) = w
T * (1/30 + 1/20) = 1
T * (20/600 + 30/600) = 1
T * (50/600) = 1
T = 600/50
T = 12 min

Thus, it takes 12 minutes for them to complete the newpaper delivery together...

Answer 6

Let's just say Shaq does 1/30th of the job each minute
Kobe does 1/20th of the job each minute.

We want to do the whole job at some time which we'll call T.

How much work can we do per minute?

Well, that's just 1/20th plus 1/30th of the job per minute, which is 5/60th of the job.

So, the whole job will be done when T times 5/60th = 1 (one job done).

Answer 7

let total work done be x
therefore shaquille takes 30 minutes to do x work
by applying untitary method
work done by him in 1 minute = x/30
similarly
work done by kobe in 1 minute = x/20

now, suppose both work together
work done by both in 1 minute =x/20 + x/30
= 5x/60 =x/ 12

that means they both do x/ 12 of the work in 1 minute..........
so u can easily find out how much time is taken to do the entire work

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(if you still can't work it out, ans is x/(x/12) = 12 minutes

Answer 8

the suited element on your son to do, is bypass returned to the instructor and ask for extra help with this...because it would be extra advantageous for him, fairly than have somebody else do it for him..