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# FB Friends

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Ani has 61 friends on Facebook, and gets 10 new friends per day.

Meanwhile, Magali has 82 friends, and gets 3 new friends per day.

If both Ani and Magali continue getting friends at the same rate, how many days will it take for them to have the same amount of friends, and how many friends must they BOTH have to achieve this?

Oct 12, 2018
edited by Guest  Oct 12, 2018

#1
+3

We want to solve this

61 + 10D  = 82 + 3D     where D is the number of days we are looking for

subtract 3D, 61 from  both sides

7D  = 21    divide both sides  by 7

D  = 3  =   number of days it will take to have the same number of friends

And the number of friends both them will have  is just twice the number of friends that either will have  =  2 [  82 + 3*3]   =  2 [ 82 + 9 ]  =   2 [ 91  ] =    182   Oct 12, 2018
#2
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The days were correct, but the number of friends was incorrect.

This is for a sort of math game, Prodigy, not sure if you've ever heard of it.

The game gives pretty cryprtic hints. This is the hint for this paticular problem:

"We need to come up with 2 linear equations based off the question.

Allow y to equal the friends, and x to equal the number of days

\(y=10x+61\) is one of the equations.

Determine the other equation, then solve for x and y using substitution"

The substitution part is what's throwing me off here, I've never been able to do this properly.

Still, thanks anyway. As I said, the # of days was correct, but the friends are incorrect.

Guest Oct 12, 2018
#4
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You answer faster than me :p :(

Dimitristhym  Oct 12, 2018
#3
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I think its easy to think about it the correct answer is 3 because 1st day A(ni) will have 71 2nd day 81 and 3rd day 91 and M(agali) 1st day will have 85 2nd day 88 and 3rd 91 but in matg we write this:

a(x)= 10x + 61

m(x)= 3x + 82

10,3 is friend per day and 61,82 friend now

We wont a(x) = m(x) so

10x +61 = 3x + 82 <=>

7x= 21 so x=3 so 3 days

And the friends both is 91+91= 182 friends both!

I hope I helped you!

Oct 12, 2018
#5
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I'm not sure why you guys kept doubling the number of friends you guys originally found, I just tried 91 friends each and it was correct.

Answer: 3 days to get 91 friends each.

Thank you for the help!

Oct 12, 2018
#6
0

3 days to get TOTAL 91 each but i dont understand why you think 182 its false answer?

Dimitristhym  Oct 12, 2018
#7
+1

Well...the question is a little unclear....I took "both" to mean the sum...but maybe the question  should be "each".....

No matter....each will have 91  and  both will have 182 total   CPhill  Oct 12, 2018
#8
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Don't blame me, blame the game.

And for CPhill, when I put this:

"and how many friends must they BOTH have to achieve this?"

I figured people would assume it to mean "each", like I did.

Guest Oct 12, 2018
edited by Guest  Oct 12, 2018