Mr B has $20000 to invest. He invests part at 6% and the rest at 7%. He earns $1280 interest. How much did he invest at each of the rates?
+128406 Let x be the amount invested at 6% and (20000 - x) = the amount invested at 7%
We have this equation { Principal * Rate = Interest }
.06x + .07 ( 20000 - x) = 1280 simplify
.06x + 1400 - .07 x = 1280
-.01x + 1400 = 1280 subtract 1400 from both sides
-.01x = -120 divide both sides by -.01
x = $12000 = amt at 6%
20000 - x = $ 8000 = amt at 7%
