IKMC 2027 - Grades 3-4 - Self-study SET 8 - Thematic Batch 3 Question 5

Worker bees are building a honeycomb from hexagonal cells, as shown. On day 1 they build 1 cell; on day 2 they add 6 cells. If they continue in the same way, how many cells does the honeycomb have on day 4?