ParHow to calculate a weighted average
Enter each value with its weight, then gx̄w6 gives the weighted mean.
Problem
You bought 100 shares at $42.50, 250 at $39.80 and 150 at $45.10. What’s your average price per share?
Keystrokes
- fΣSST
Clears the statistics registers.
- 42.5ENTER100Σ+
The price, then its weight, the number of shares.
- 39.8ENTER250Σ+
- 45.1ENTER150Σ+
- gx̄w6
The weighted average.
Answer
Your average price is $41.93 a share.
Why it works
With the value in Y and the weight in X, Σ+ adds up the weights and the products of value times weight. gx̄w6 divides one by the other.
The same steps give a grade point average, value as the grade and weight as the credits, or the average rate across several loans, weighted by balance.