CPhill

Oops...thanks, Alan...

Since it's compounded quarterly, the interest rate per period is 12% / 4  = 3% = .03

Sa_c = 2 * pi * r * h       where  r is the radius and h is the height.....

[ In essence, we just "stacking" a bunch of like "perimeters" on top of each other...!!!]

Let x be the number that paid 35 pounds and y be those that paid 45 pounds

So we have this system of equations

x + y = 500

35x + 45y = 20500

And using the first equation, we can rearrange it as y = 500 - x....and subbing this in for y in the second equation, we have

35x + 45(500 - x) = 20500   simplify

35x + 22500 - 45x = 20500  combine like terms on the left side

-10x + 22500 = 20500       subtract 22500 from each side

-10x = -2000    divide both sides by -10

x = 200.....and this is the number of people who paid 35 pounds

One left.......two remained....!!!

[1 + 6/13]  - 18/19

19/13 - 18/19 =      (the common denominator = 247)

[361 - 234] / 247 =

127/ 247

I assume this is (3^2)^x = 195  ??? if so, we have

9^x = 195     take the log of both sides

log 9^x  = log 195   and by a log property, we have

x log 9  = log 195    divide both sides by log 9

x = log 195 / log 9  = about 2.4

We don't see anything, here......(????)