Percentage word problem

[Astromars]

This problem confuses me and id like some help please.

Let 48 be the amount of pencils and 75% of tbe pencils are with black lead. (36)
How many black pencils would need to be added in order to make it 80%?

I cannot seem to figure it out. The answer is 60. But i do not know how to get there.
Please and thank you.

 

[Deleted member 4993]

This problem confuses me and id like some help please.

Let 48 be the amount of pencils and 75% of tbe pencils are with black lead. (36)
How many black pencils would need to be added in order to make it 80%?

I cannot seem to figure it out. The answer is 60. But i do not know how to get there.
Please and thank you.

How many black pencils would need to be added in order to make it 80%?

lets assume that:

additional # of black pencils added = b

then

(36 + b)/(48 + b) = 0.8 ..................... solve for 'b'.

The given answer is incorrect for the question asked.

Please share your work - so that we can catch your mistake (if any).

 

[Astromars]

Doesnt that leavw us with
(36+b)=(.8)(48+b)
How do i get b=12?

 

[Deleted member 4993]

Doesnt that leavw us with
(36+b)=(.8)(48+b)
How do i get b=12?

(36+b)=(.8)(48+b)................. distribute

36 + b = 0.8 * b + 0.8 * 48 ...................continue

 

[Astromars]

Ok i got it figured out
X+36=.8x+38.4
Cancel like terms

.2x=2.4
X=2.4(5)=12

36+12=48
----------------
48+12=60
48/60=0.8
Thank you

 

[Deleted member 4993]

Ok i got it figured out
X+36=.8x+38.4
Cancel like terms

.2x=2.4
X=2.4(5)=12

36+12=48
----------------
48+12=60
48/60=0.8
Thank you

Good Work!!