ANSWER

Step-by-step explanation
From the given data;
The ratio of the grandmother who buys lunch : all grandmother is;

To calculate the corresponding values of grandmothers who buys lunch and all grandmother;
For the 3rd column;
When all grandmother is 150.
The grandmothers who buy lunch will be;

Hence the ratio;

also, the next column;

For all grandmother, add 50 to 150

Hence, the ratio equals;

The next column for grandmothers who buy lunch;

For all grandmother;

The ratio;

About 200