Question

This diagram shows part of a design made by using toothpicks to form triangles. The top level uses 3 toothpicks. The second level uses 6 toothpicks. The third level uses 9 toothpicks, and so on. If you decide to continue the design so that it has 7 levels, how many toothpicks do you need altogether

Answer 1

the answer to this problem is simple to find the answer we must see the keywords in the sentence on of is how many which can mean addition/multiplication so here the problem is increasing in a rate of 3 3x1=3
 3x2=6 3x3=9 and so on 3x7=21 your answer is 21