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Roberto invested some money at 7%, and then invested $2000 more than twice this amount at 11%. His total annual income from the two investments was $3990. How much was invested at 11%?

Answer 1

Julia Adams

#$13000#

Let the principle sum be #P#

#(7P)/100 + (11(2P+2000))/100 = 3990#

Multiply both sides by 100

#(7P) + 11(2P+2000) = 399000#

#7P+22P+22000=399000#

#29P=377000#

#P=$13000#

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Answer 2

Isaiah Anthony

Let x be the amount invested at 7%. Then the amount invested at 11% is (2x + 2000). The total income from the two investments is 0.07x + 0.11(2x + 2000) = 3990. Solving this equation yields x = 10000. Therefore, the amount invested at 11% is 2(10000) + 2000 = $22000.

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Answer from HIX Tutor

When evaluating a one-sided limit, you need to be careful when a quantity is approaching zero since its sign is different depending on which way it is approaching zero from. Let us look at some examples.