Moe invested $18,000. Part of it was invested at 3% annual simple interest and the best was invested at 4%.?

Lizzette Wendroth: This can be solved mentally without the help of any equation etc.if he would have have invested the whole anount at3% interest,it would have fetched him$540 interest.But he receives $110 more because he invested some part @4%For every $1 more,he has to invest $100 @4%so for $110 more ,he had to invest 110*100 or $11000 @4%The remaing amount of $7000 was invested @3%...Show more

Ilana Gaster: This is a system.x=3% investmenty=4% investmentx+y=180000.03x+0.04y=650You can solve this a lot of different ways.Some people use substitution, but I get rid of the decimals and do linear combination.100(0.03x)+100(0.04y)=100(650)3x+4y=65000 Multiply the first equation by -3-3x-3y=-54000Add the two togethery=11000, so x=7000$11,000 @4%$7,000 @3%...Show more