2,000 students take a test whose marks are normal with mean 60 and standard deviation 12. About how many score more than 78? (Take $P(0 < Z < 1.5) = 0.4332$.)

Explanation

1. 01

   $z = \frac{78 - 60}{12} = 1.5$, and $P(Z > 1.5) = 0.5 - 0.4332 = 0.0668$.

2. 02

   $0.0668 \times 2{,}000 = 133.6$, about 134 students.