The formula used to solve these problems is:
Principal × Interest Rate × Time = Simple Interest (the interest rate needs to be converted to a decimal and the time needs to be converted to years)
1) 2000 × 0.035 × 3 = $210
#6 and #12 are solved the same way
2) 1250 × _____ × 4 = 350
divide both sides by 1250 and by 4 --> 0.07 = [tex]\dfrac{350}{1250\times 4}[/tex]
convert the decimal to a percent --> 0.07 = 7%
#5 & #11 are solved the same way
3) 500 × 0.045 × _____ = 157.50
divide both sides by 500 and by 0.045 --> 7 = [tex]\dfrac{157.50}{500\times 0.045}[/tex]
#8 and #10 are solved the same way
4) ______ × 0.05 × 4.5 = 2115
divide both sides by 0.05 and by 4.5 --> 940 = [tex]\dfrac{2115}{0.05\times 4.5}[/tex]
#7 and #9 are solved the same way
See Table Below for answers:
[tex]\begin {array}{l|l|l||l}Principle&Interest\ Rate&Time&Simple\ Interest\\1.\ \$2000&3.5\%=0.035&3\ years&\boxed{\$210}\\2.\ \$1250&\boxed{7\%}=0.07&4\ years&\$350\\3.\ \$500&4.5\%=0.045&\boxed{7\ years}&\$157.50\\4.\ \boxed{\$940}&5\%=0.05&4.5\ years&\$2,115\\5.\ \$12,000&\boxed{4.5\%}=0.045&2\ years&\$1,080\\6.\ \$1800&7.5\%=0.075&0.5\ years&\boxed{\$67.50}\\7.\ \boxed{\$307.50}&6\%=0.06&4\ years&\$73.80\\8.\ \$8500&6.5\%=0.065&\boxed{12\ years}&\$6630\\\end{array}[/tex][tex]\begin {array}{l|l|l||l}9.\ \boxed{\$4000}\quad &3.5\%=0.035&5\ years&\$700\\10.\ \$3300&4.75\%=0.0475&\boxed{2\ years}&\$ 313.50\\11.\ \$6800&\boxed{2.5\%}=0.025&16\ years&\$2720\\12.\ \$2400&5.5\%=0.055&2.5\ years&\boxed{\$330}\\\end{array}[/tex]
