Write an arithmetic sequences that has three arithmetic means between 155 and 215

The explicit formula for arithmetic is given by:

an = a1 + (n-1) d

In the current case,

a5 = 215

a1 = 155

n = 5

Substituting;

215 = 155 + (5-1) d

60 = 4d

d = 60/4 = 15

Then,

a1 = 155

a2 = 155 + (2-1) 15 = 170

a3 = 155 + (3-1) 15 = 185

a4 = 155 + (4-1) 15 = 200

a5 = 215

Therefore, the sequence is:

155,170,185,200,215