A grocery clerk sets up a display of 12-pack cartons of cola. There are 15
cartons at the base of the triangle and one at the top. How many cartons of
cola are needed for the complete display?
Step-by-step explanation: Since, the grocery clerk displays 15 cartons at the base of the triangle and one at the top. Therefore, one carton is reduced at previous step and so on. Since, this series is in arithmetic progression. Therefore, 120 cartons are needed for the complete display.
