+68 To go to sleep, Oliver counted by 6s starting from 15. Thus the first few numbers he named were
15,21,27,33...
The last number he named before he fell asleep was 363. How many numbers did Oliver name?
[L - F] / D + 1=N, where L=Last term, F=First term, D=Common difference, N=Number of terms
[363 - 15] / 6 + 1 =59 terms or numbers that Oliver counted.
+9481 If he named 1 number, then the last number he named would be 15
If he named 2 numbers, the last number he named would be 15 + 6
If he named 3 numbers, the last number he named would be 15 + 6 + 6
If he named 4 numbers, the last number he named would be 15 + 6 + 6 + 6 which is 15 + 6(4 - 1)
So... if he named n numbers, the last number he named would be 15 + 6(n - 1)
They tell us the last number he named was 363 . So..
363 = 15 + 6(n - 1) Subtract 15 from both sides.
348 = 6(n - 1) Divide both sides by 6 .
58 = n - 1 Add 1 to both sides.
59 = n
