What are we supposed to find
If your looking for basically the definition of ratio it means, lets say we have 2 can of milks, and 3 cans of cookies, if it asks find the ratio of milks first then cans it is 2:3, or if it asks find the ratio of cans of milk to cookies, which is 3:2 or part to whole which means 3+2 or 2+3= 5 is whole and if they say part would be milk then 2:5 or if its cans of cookies to whole its, 3:5. I hope this helps ask me anything that you didn’t understand!
Since it is looking for the sum
at S3, replace n with 3 , 2, and 1 , solve the equation and add all of answers together
when s = 3 the equation becomes 5(1/3)^3-1
5(1/3)^2 = 5/9
when s = 2 the equation becomes 5(1/3)^2-1
5(1/3)^1 = 5/3
when s = 1 the equation becomes 5(1/3)^1-1
5(1/3)^0 = 5
5/9 + 5/3 + 5 = 65/9
the answer is the 3rd choice
Answer: He made $90 last week.
Assumption :
Let, Luis made $X last week.
He made $72 this week which is 80% of $X that he made last week
⇒ X * 80% = 72
⇒ X * 80/100 = 72
⇒ X = (72 * 100)/80
⇒ X = 90
Therefore, he made $90 last week.
To remember :
While solving this type of problems, be careful to understand which one of last time and current time is not given; just assume that one and input other conditions, the problem will be solved.
