943 Example 7.10. Interpolate by means of Gauss's backward formula, the population of a town for the year 1974, given that: Year 1939 1949 1959 1969 1979 1989 Population 12 15 20 27 39 52 (in thousands) 9. 19 943 Example 7.10. Interpolate by means of Gauss's backward formula, the population of a town for the year 1974, given that: Year 1939 1949 1959 1969 1979 1989 Population 12 15 20 27 39 52 (in thousands) 9. 19