If all 3 angles of a Triangle MUST equal 180°, then we know that we use the equation (for this triangle) to find the angle measurements as (180-90)/2 which means we are dividing 90/2 which is 45° for each angle. But these angles are different measures, so we have to guess upon this and say that YOUR ANSWER IS D
12x+12 step by step below
P(at least 5 rolls until 1) = P(4 rolls are not 1) = 5/6 x 5/6 x 5/6 x 5/6 = 0.4823 (4sf)
Fewer than 7 rolls to get second 1 after first takes 3 rolls means second occurs on 4th, 5th or 6th roll
The probability of each of these is 1/6, 5/6 x 1/6 and 5/6 x 5/6 x 1/6 respectively.
P(second 1 on 4th, 5th or 6th roll) = 1/6 + 5/36 + 25/216 = 91/216 = 0.4213 (4sf)
