Since the mean is 100 and the SD is 20. Note for 140 IQ score, you are 2

standard deviations above the mean.

That means you scored higher than 97.5% of the people who took the IQ

test.

That is 97.5% of the area under the normal curve. Remember the Empirical

Rule, 68-95-99.7

That is, 68% of the data is within one SD, 95% of the data is within 2 SD,

and 99.7% of the data is within 3 SD. Therefore, 50+34+13.5=97.5.

Suppose someone had a 180 IQ. That means they would be 4 SD above

the mean. That would correspond to .999968328283

That means they would score higher than 99.9968% of the others.

If 1,000,000 took the test, that means only about 32 out of 1 million

would score as high or higher.

For your 140 score, if 1 million took the test, about 25,000 out of the

million would score as higher or higher than 140.

See now a wee bit better?.