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For sum to to be even, either both numbers need to be even or both need to be odd.

Case 1: Both Even = 6C2 = 15
Case 1: Both Odd = 4C2 = 6
Total Cases = 10C2 = 45
Favourable Cases = 15+6 = 21
P = 21/45 = 7/15


Or doing it your way, we pick 1 even and 1 odd = 6C1 * 4C1 = 24
Total Cases = 10C2 = 45
P(Sum odd) = 24/45 = 8/15
P(Sum Even) = 1-8/15 = 7/15
Iserhard
Hello, one question

Can we do 1 - Prob (EO)?

Idk what Im doing wrong here.

1 - (4/10 * 6/9) =

(1 - 4/15) = 3/5

Cheers
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Okay. I have another way for this one.

Using simple/random numbers, I quickly calculated to the side, what kind of numbers (even and odd) added together will give me an even sum. I determined (1) even # + (1) even # = even number and (1) odd # + (1) odd # = even number.

1. Set up slots - (1) even # + (1) even # = even number CASE:

6 (chances i pick an even number)/10 (total number of integers in the set) * 5 (chances i pick an even number NOW - since I am not replacing my first pick)/9 (total number of integers NOW in the set) = 15/45

2. Set up slots - (1) odd # + (1) odd # = even number CASE:

4 (chances i pick an odd number)/10 (total number of integers in the set) * 3 (chances i pick an odd number NOW - since I am not replacing my first pick)/9 (total number of integers NOW in the set) = 6/45

3. Total probability (Addition)

15/45 + 6/45 = 21/45 = 7/15!!
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