A12-ft-by-15-ft rectangular swimming pool has a 3-ft-wide no-slip surface around it. what is the outer perimeter of the no-slip surface? a. 78 ft. b. 78 ft2. c. 198 ft. d. 198 ft2

we are given with a swimming pool with dimensions 
12-ft-by-15-ft. given that there is a 3-ft-wide no-slip surface around it, the new dimensions now become (12+3+3) or 18 ft by (15+3+3) or equal to 21 ft. The perimeter is the sum of the sides of the new rectangle. Perimeter is equal to 18+ 18 + 21 + 21 or equal to 78 feet

Multiply 9 and 67. then multiply 3 with 67. lastly the answer that you got for 9x67 is to be subtracted by the answer you got for 3x67

, and

for

step-by-step explanation:

we can analyze the pattern at which the terms increase. let us denote , , , so that we can call

1 the 1st term, 3 the 2nd term, 6 the 3rd term,etc.

note the following:

from the 1st term (1) to the 2nd term (3), we go up by 2,from the 2nd term (3) to the 3rd term (6), we go up by 3from the 3rd term (6) to the 4th term (10), we go up by 4, andfrom the 4th term (10) to the 5th term (15), we go up by 5.

the pattern: to get the next term value, we just add the next term number (e.g. 1st, 2nd, to the previous term value (term values are the given numbers in the question, 1, 3, 6, 10, 15,

from , to get to , we add

from , to get to , we add

etc.

we need to form a recursive formula, a formula that has the next term as a function of the previous term. so a possible recursive formula can be

, and for