7
algebra

You have $1000 to invest. Part at 5% interest and part at 8%. If the total interest is $68, how much was invested at 8%?

A

500

B

600

C

800

D

400

Correct Answer: B

Choice Dhoice A is the correct answer.

  1. Define: 8% = xx, 5% = 1000−x1000 - x.
  2. Equation: 0.08x+0.05(1000−x)=680.08x + 0.05(1000 - x) = 68
  3. Simplify: 0.08x+50−0.05x=680.08x + 50 - 0.05x = 68
  4. Combine: 0.03x=180.03x = 18
  5. Divide by 0.03: x=600x = 600
  6. Verify: 0.08(600)+0.05(400)=48+20=680.08(600) + 0.05(400) = 48 + 20 = 68 ✓

Choice Dhoice D is incorrect because this is the amount at 5%.

Choice Dhoice C is incorrect because calculation error.

Choice Dhoice B is incorrect because calculation error.

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