TTGWD11-13

echo19872010

Q13:

On a certain day, Tim invested $1,000 at 10 percent annual interest, compounded annually, and Lana invested $2,000 at 5 percent annual interest, compounded annually.
The total amount of interest earned by Tim’s investment in the first 2 years was how much greater than the total amount of interest earned by Lana’s investment in the first 2 years?



A.
$5

B.
$15

C.
$50

D.
$100

E.
$105

Answer: A算了N遍还是得105，

  
能不能帮着算一下啊？我那里错了？1000*（1+0。1）^2-1000-2000*(1+0.05^2)

nieyuhang

should be 1000*（1+0。1）^2-1000 减去2000*(1+0.05)^2-2000

gmatmba

First year's earning for Tim are: 1000*0.1=100

second year's earing for Tim are: (1000+100)*0.1=110

So two year's total earning are 100+110=210

First year's earning for Lana are: 2000*0.05=100

Second year's earing for Lana are (2000+100)*0.05=105

total earning for Lana are 205

The difference between Tim and Lana are 210-205=5

missouyangs

楼主错在题目要求的是The total amount of interest，利息，而不是本金加上利息，S＝P（1＋i）^n这个公式算的是本息和，所以应该再减去本金，也就是1楼说的