by **Rafael_examPAL** » Tue Jul 04, 2017 11:17 am

Hey Jamesk,

So, there are 2 ways to solve this question and you need to find the one that is best for you.

The first method uses PRECISE calculations:

let M = total sold by Mark (M=>1)

let A = total sold by Ann (A=>1)

then: M= n-10

A= n -2

And: M + A < n

(n-10) + (n-2) < n

2n -12 <n

n<12

--> n=11! (A)

or, the second method is the ALTERNATIVE approach, wherein we will use the answers given and some LOGIC:

I will choose any of the answers, say (C), n=13, and see if it fits the criteria:

If n=13.

Then A = 13-10 =3 (=>1 :so far so good)

M = 13 - 2 = 11(=>1)

Then, A + M = 3+11=14, but then 14 > n. so this doesn't work.

lets try a smaller answer, (A), n =11:

Then A = 11-10 =1 (=>1 :so far so good)

M = 11 - 2 = 9 (=>1)

Then, A + M = 1+9 =10, which then A+M (=10) < n (=11). so this does work!

Note: I have used the PAL (Precise/Alternative/Logical) system to generate these two solutions.