According to the manual, a battery in a cellular phone loses 2% of its charge each day. Assume the battery is 100% charged.

a) Write an equation to represent the percent charge, P, as a function of the number of days, d, since the battery was charged.

b) Determine the number of days until the battery in only 50% charged.

a) Write an equation to represent the percent charge, P, as a function of the number of days, d, since the battery was charged.

b) Determine the number of days until the battery in only 50% charged.

Guest Mar 9, 2012

#1**0 **

P(d)=100-(1.02)^d

[input]plot( 100-(1.02)^d, d=0..200 )[/input]

100-(1.02)^d = 50

-(1.02)^d = 50-100

(1.02)^d = 50

log( 50, 1.02 )

[input]log( 50, 1.02 )[/input]

rimmy:a) Write an equation to represent the percent charge, P, as a function of the number of days, d, since the battery was charged.

P(d)=100-(1.02)^d

[input]plot( 100-(1.02)^d, d=0..200 )[/input]

rimmy:Determine the number of days until the battery in only 50% charged.

100-(1.02)^d = 50

-(1.02)^d = 50-100

(1.02)^d = 50

log( 50, 1.02 )

[input]log( 50, 1.02 )[/input]

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Mar 9, 2012