maths mc X2

1.
μ = 74
σ = 7
z = (60 - 74)/7 = -2

no. of failed candidates
= (50% - 95%/2)(2000)
= 50

-> Answer is B.

2
angle BAT + angle BCT
= (90 - angle OAB) + (90 - angle OCB) ( tangent perpendicular to radius)
= 180 - angle OAB - angle OCB (i)

angle AOC = 80
Reflex angle (反角) AOC = 360 - 80 = 280
angle ABC = 280/2 = 140 ( angle at center twice angle at circumference)

angle OAB + angle OCB + angle AOC + angle ABC = 360
angle OAB + angle OCB = 360 - 140 - 80 = 140

By (i).
angle BAT + angle BCT = 180 - 140 = 40

-> Answer is A.