PLEASE HELP ASAP!!! Phyllis invested 42000 dollars, a portion earning a simple interest rate of 4 percent per year and the res

Question

PLEASE HELP ASAP!!!
Phyllis invested 42000 dollars, a portion earning a simple interest rate of
4 percent per year and the rest earning a rate of 7 percent per year. After one year the total interest earned on these investments was 2220 dollars. How much money did she invest at each rate?
DONT SAY I DONT KNOW

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Doris 5 years 2021-09-04T11:37:24+00:00 1 Answers 12 views 0

Answers ( )

  1. thienthi
    0
    2021-09-04T11:39:09+00:00
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    Answers:

    • 24000 dollars invested at 4%
    • 18000 dollars was invested at 7%

    ======================================================

    Work Shown:

    x = amount invested at 4%

    If she invests x dollars at 4%, then the rest (42000-x) must be invested at the other rate of 7%

    She earns 0.04x dollars from that first account and 0.07(42000-x) dollars from the second account

    This means we have

    0.04x+0.07(42000-x)

    0.04x+0.07*42000-0.07x

    0.04x+2940-0.07x

    -0.03x+2940

    This represents the total amount of money earned after 1 year.

    We’re told the amount earned in interest is $2220, so we can say,

    -0.03x+2940 = 2220

    -0.03x = 2220-2940

    -0.03x = -720

    x = -720/(-0.03)

    x = 24000 dollars is the amount invested at 4%

    42000-x = 42000-24000 = 18000 dollars was invested at 7%

    ———————-

    As a check, we can see that

    18000+24000 = 42000

    and also

    0.04x = 0.04*24000 = 960 earned from the first account

    0.07*18000 = 1260 earned from the second account

    1260+960 = 2220 is the total interest earned from both accounts combined

    This confirms our answers.

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Giải phương trình 1 ẩn: x + 2 - 2(x + 1) = -x . Hỏi x = ? ( )