Answer:
125
Step-by-step explanation:
For arithmetic sequence: aₙ = a₁ + (n-1)d Sₙ = n/2 * (a₁ + aₙ)
a1+a4+a7+a10 = a₁ + (a₁ + 3d) + (a₁ + 6d) + (a₁ + 9d) = 4a₁ + 18d = 2 * (2a₁ + 9d)
2 * (2a₁ + 9d) = 50
2a₁ + 9d = 25
a1+a2+a3...+a10 = 10/2 * (a₁ + a₁₀) = 5 * (a₁ + a₁ + 9d) = 5 * (2a₁ + 9d)
a1+a2+a3...+a10 = 5 * 25 = 125
