row n has 35-4(n-1) = 39-4n plants
39 = 4*9+3, so the last row will have 3 plants
There are 10 rows, so
S10 = 10/2 (3*3 + 9*4)
A gardener is making a triangular planting, with 35 plants in the
front row, 31 in the second row, 27 in the third row, and so on. If
the pattern is consistent, how many plants will be there in the last
row? How many plants are there?
1 answer