Jawapan

2016-01-19T15:13:00+08:00
315 + 320 + 325 + 330 + 335 + 340 + 345 + 350 + 355 + 360 + 365 + 370 + 375 + 380 + 385 + 390 + 395 + 400 + 405 + 410 + 415 + 420 + 425 + 430 + 435 + 440 + 445 + 450 + 455 + 460
= 11 625
1 5 1
2016-01-22T00:30:52+08:00
A = 315
d = 5

Tn = 460
a + (n-1)d = 460
315 + (n-1)5 = 460
5(n-1) = 145
n-1 = 145/5
n = 30

Sn = n/2 [2a + (n-1)d]

S30
= 30/2 [2(315) + 29(5)]
= 15 (630 + 145)
= 11625