What is the percent of increase from $147 annually to $414?

1 Answer
May 23, 2016

color(red)("The time span not defined as 1 year")
For 1 year only color(blue)(-> "percentage is " 187.5%)
Or simple interest over whole period
'.....................................................
For more than 1 year where n is number of years
and annually compounded interest.

" "color(blue)(x%=log^(-1)((log(414)-log(144))/n + 2) - 100)

Explanation:

color(red)("You have not stated the number of years.")
color(red)("The use of the word 'annually' implies more than 1 year")

Let the number of years be n

" "$144(1+x/100)^n=$414

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Suppose the number of years is 1 then")

" "144+(144xx ?/100)=414

color(brown)("Subtract 144 from both sides")

" "144xx ?/100=270

color(brown)("Multiply both sides by "100/144)

color(blue)(" "?%=270xx100/144 = 187.5%)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(blue)("Suppose "n>1)color(magenta)(" "->" Needs algebra")

color(brown)("Notice that " (1+x/100) ->((100+x)/100))

color(brown)("Taking logs of both sides")

" "log($144)+nlog((100+x)/100)=log($414)

" "nlog((100+x)/100)=log(414)-log(144)

" "log((100+x)/100)=(log(414)-log(144))/n

" "log(100+x)-log(100)=(log(414)-log(144))/n

" "log(100+x)=(log(414)-log(144))/n + log(100)

'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
color(brown)("But "log(100)=2

" "log(100+x)=(log(414)-log(144))/n + 2

" "100+x=log^(-1)((log(414)-log(144))/n + 2)

" "color(blue)(x%=log^(-1)((log(414)-log(144))/n + 2) - 100)