Mr. Williams can grade 50 essays in 7 hours. His assistant, Mr. Wilfred, can do the same job in 14 hours. His other assistant, Ms. Stealth, can grade 25 essays in 6 hours. How long will it take them to grade 200 essays if all three work together?

13.44 or 13 11/25 hours

Step-by-step explanation:

First use this format: number of essays/hours

- they are asking if all three work together, how many hours would it take, so this means addition:

50/7 + 50/14 + 25/6 = 200/x

Second, solve:

- least common multiple: 42

300/42 + 150/42 + 175/6 = 200/x

625/42 = 200/x

- cross-multiply

625x = 8,400

x = 336/25 = 13 11/25 = 13.44 (any one of these answers would work)

answer: 25 is the correct answer

step-by-step explanation:

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

note the following:

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for