(ab)n=anbn......................................
12 red and 36 blue pens. 12/36 = 3/9 so the ratio is correct, and 12+36 = 48 workers.

solve for "r"
notice, the "r" value, goes in the equation as a decimal, so 5% is really 5/100 or 0.05 25% is 0.25 and so on
so... the "r" that you'll get, will be a decimal value, multiply that by 100, and you'll get the percentage notation of it
![\bf 6,000=2,500\left(1+\frac{r}{4}\right)^{4\cdot 10}\implies\cfrac{6000}{2500}=\left(1+\frac{r}{4}\right)^{40} \\ \quad \\ \cfrac{12}{5}=\left(1+\frac{r}{4}\right)^{40}\impliedby \textit{now, taking root }\sqrt[40]{\qquad } \\ \quad \\ \sqrt[40]{\cfrac{12}{5}}=\sqrt[40]{\left(1+\frac{r}{4}\right)^{40}}\implies \sqrt[40]{\cfrac{12}{5}}=1+\cfrac{r}{4} \\ \quad \\ \sqrt[40]{\cfrac{12}{5}}-1=\cfrac{r}{4}\implies 4\left( \sqrt[40]{\cfrac{12}{5}}-1 \right)=r \\ \quad \\ ](https://tex.z-dn.net/?f=%5Cbf%206%2C000%3D2%2C500%5Cleft%281%2B%5Cfrac%7Br%7D%7B4%7D%5Cright%29%5E%7B4%5Ccdot%2010%7D%5Cimplies%5Ccfrac%7B6000%7D%7B2500%7D%3D%5Cleft%281%2B%5Cfrac%7Br%7D%7B4%7D%5Cright%29%5E%7B40%7D%0A%5C%5C%20%5Cquad%20%5C%5C%0A%5Ccfrac%7B12%7D%7B5%7D%3D%5Cleft%281%2B%5Cfrac%7Br%7D%7B4%7D%5Cright%29%5E%7B40%7D%5Cimpliedby%20%5Ctextit%7Bnow%2C%20taking%20root%20%7D%5Csqrt%5B40%5D%7B%5Cqquad%20%7D%0A%5C%5C%20%5Cquad%20%5C%5C%0A%5Csqrt%5B40%5D%7B%5Ccfrac%7B12%7D%7B5%7D%7D%3D%5Csqrt%5B40%5D%7B%5Cleft%281%2B%5Cfrac%7Br%7D%7B4%7D%5Cright%29%5E%7B40%7D%7D%5Cimplies%20%5Csqrt%5B40%5D%7B%5Ccfrac%7B12%7D%7B5%7D%7D%3D1%2B%5Ccfrac%7Br%7D%7B4%7D%0A%5C%5C%20%5Cquad%20%5C%5C%0A%5Csqrt%5B40%5D%7B%5Ccfrac%7B12%7D%7B5%7D%7D-1%3D%5Ccfrac%7Br%7D%7B4%7D%5Cimplies%204%5Cleft%28%20%5Csqrt%5B40%5D%7B%5Ccfrac%7B12%7D%7B5%7D%7D-1%20%5Cright%29%3Dr%20%5C%5C%20%5Cquad%20%5C%5C%0A)
If AP and PB are in a 1:2 ratio, it means that PB is twice AB.
So, AP must fit three times into AB, meaning that P must be at one third of the way between A and B.