Ryan was 8 when his parents invested $4000 in a certificate of deposit that pays 6%. If Ryan leaves the account alone until it reaches $10,000, how old will he be?

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Answer 1 · 2017-10-22T14:17:19

about #24#

Compund Interest Formula :

#"Amount"="Principle"*(1+"Rate")^"Time"#

Here,

#$10000=$4000 *(1+6%)^"t"#

#=($10000)/($4000)= *(1+0.6)^"t"#

#=2.5=1.06^t#

Take log of both sides:

#log(1.06^x)=log(2.5)#

#=x*log(1.06)=log(2.5)#

#=x=log(2.5)/log(1.06)#

#=x~~15.73#

#therefore# Ryan will be #8+15.73~~24# years old then.