SOLUTION: Luis invested $6000 in two different accounts. One earned 4% and the other earned 7%. He earned a total of $375 in interest in one year. How much was invested in each account?
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Question 1149483: Luis invested $6000 in two different accounts. One earned 4% and the other earned 7%. He earned a total of $375 in interest in one year. How much was invested in each account? Found 2 solutions by josmiceli, greenestamps:Answer by josmiceli(19441) (Show Source):
You can put this solution on YOUR website! For the 2 accounts = amount invested in 4% account = amount invested in 7% account = interest from 4% account = interest from 7% = 1 year
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For 4% account:
(1)
For 7% account:
(2)
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By substitution:
(2)
(2)
(2)
and
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$1,500 = amount invested in 4% account
$4,500 = amount invested in 7% account
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check:
(1)
(1)
(1)
and
(2)
(2)
(2)
(2)
OK
If an algebraic solution is not required, then compare the amount of work required by this alternative method with that required with the standard algebraic solution shown by the other tutor.
$6000 all at 4% --> $240 interest
$6000 split between 4% and 7% --> $375 interest
$6000 all at 7% --> $420 interest
$375 is 3/4 of the way from $240 to $420. ($240 to $375 is $135; $240 to $420 is $180; 135/180 = 3/4. Picture the three numbers on a number line if it helps you see the 3/4.)
That means 3/4 of the investment is at the higher rate.
ANSWER: 3/4 of $6000, or $4500, at 7%; the other $1500 at 4%.
