Algebra word problem?

bravo-my-friendbravo-my-friend
in Science & Mathematics

Please show work if you can:

1) $5,900 is invested, part at 11% and part of it at 6%. For a certain year, the total yield is $509.00. How much was invested at each rate?

2) How much 75 octane and 90 octane gas is needed to make 15 gallons of 87 octane gas?

Comments

  • polygonpolygon

    Let x = amount invested at 11%

    1)...A1 = x(1.11)

    2)...A2 = (5900 - x)(1.06)

    2) ...A2 = 6254 - 1.06x

    Total return = 5900 + 509 = 6409

    A1 + A2 = 6409

    3) 6409 = 1.11x + 6254 - 1.06x

    155 = 1.05x

    x = $147.62 invested at 11%

    $361.38 invested at 6%

    -----------------------------------------------

    Let x = gallons of 75 octane gas

    75x + 90(15 - x) = 87*15

    75x + 1350 - 90x = 1305

    -15x = - 45

    x = 3 gallons of 75 octane

    12 gallons of 90 octane

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