## Interpolation

Interpolation uses a linear model to estimate the value of a variable on an interval.
Suppose variables
$A, \;$
are measured and take the values
$(A,B)=(20,35), \; (30, 60)$
.
It is required to find the value of
$B$
at
$A=23$
. Using the linear model
$\frac{B-B_1}{A-A_1}=\frac{B_2-B_1}{A_2-A_1}$

gives
$\frac{B-35}{23-20}=\frac{60-35}{30-20} \rightarrow B= \frac{60-35}{30-20} \times (23-20)+35=42.5$