Question

percentage?
How would I work this out? I don't need an answer just an equation if possible.

ex:
A cell phone loses 4% charge per hour with normal use. Assuming you start with an 88% charge, how long will it take for your bettery to completely drain?

Answer 1

say, \(t\) = number of hours after u start.

Answer 2

so, after \(t\) hhours, there will be charge of : \(88-4t \) percent

Answer 3

to completely drain the battery, set it equal to 0 and solve \(t\)

Answer 4

\(88-4t = 0\)

solve \(t\)

Answer 5

see if that makes some sense @MyKidzRKute

Answer 6

ok so setting to 0 i got, empty battery+0. Now i start with 88% so i'm so tempted to make this equation a fraction, say 88/100. Why is that not necessary?

Answer 7

your start point is 88%
every hour is "eating away" 4% per normal use

so as ganeshie8 said, when the battery is totally dead, the charge will be 0%
so we can afford to leave out the % part, since all values represent the same unit

so 88 - 4(t) = 0 <-- 0 means at that point, when "t" is that value, the battery is dead
and at every "t" that passes, 4t is being eaten away from 88, till it equals 0

Answer 8

btw, about the acres and livestock before, in case you missed it -> \(\bf 2\cfrac{2}{3}+8\cfrac{1}{2}+6\cfrac{3}{4}+3\cfrac{1}{4}+4\cfrac{1}{2}\\ \quad \\\implies \cfrac{8}{3}+\cfrac{17}{2}+\cfrac{27}{4}+\cfrac{13}{4}+\cfrac{9}{2}=\cfrac{32+102+81+39+54}{12}\\ \quad \\
\cfrac{308}{12}\implies 25\cfrac{8}{12}\implies 25\cfrac{2}{3}\)

Answer 9

start wid : 88/100
every hour : 4/100
so, remaining charge after t hours : 88/100 - 4/100t

set it to 0, u wud get the same answer.

the point is, u need to convert % to decimal always.

Answer 10

*the point is, u need NOT convert % to decimal always.