$4\mathrm{.}91$ Find $j_{12}$ at which $$100$ will accumulate $$50$ interest in $4$ years $7$ months. Ans. $8\mathrm{.}88\%$

$4\mathrm{.}92$ John deposited $$1000$ three and a half years ago. He has $$1581\mathrm{.}72$ in his account now. What

rate of interest compounded semiannually did he earn on his deposit? Ans. $13\mathrm{.}54\%$

${}_2$:

$t=3\mathrm{.}5$