A man has $ 10,000 to invest. He invests $ 4000 at 5 % and $ 3500 at 4 %. In order to have a yearly income of $ 500, he must invest the remainder at
Answers:
A) 6 % B) 6.1 % C) 6.2 % D) 6.3 % E) 6.4 %
Solution:   Income from $ 4000 at 5 % in one year = $ 4000 of 5 %.   = $ 4000 × 5/100.   = $ 4000 × 0.05.   = $ 200.   Income from $ 3500 at 4 % in one year = $ 3500 of 4 %.   = $ 3500 × 4/100.   = $ 3500 × 0.04.   = $ 140.   Total income from 4000 at 5 % and 3500 at 4 % = $ 200 + $ 140 = $ 340.   Remaining income amount in order to have a yearly income of $ 500 = $ 500 - $ 340.   = $ 160.   Total invested amount = $ 4000 + $ 3500 = $7500.   Remaining invest amount = $ 10000 - $ 7500 = $ 2500.   We know that, Interest = Principal × Rate × Time   Interest = $ 160,   Principal = $ 2500,   Rate = r [we need to find the value of r],   Time = 1 year.   160 = 2500 × r × 1.   160 = 2500r   160/2500 = 2500r/2500 [divide both sides by 2500]   0.064 = r   r = 0.064   Change it to a percent by moving the decimal to the right two places r = 6.4 %   Therefore, he invested the remaining amount $ 2500 at 6.4 % in order to get $ 500 income every year.   Answer: (6.4 %)
<result>E</result>
A man has $ 10,000 to invest. He invests $ 4000 at 5 % and $ 3500 at 4 %. In order to have a yearly income of $ 500, he must invest the remainder at