Di sajikan barisan bilangan 5,10,15,20 jumlah 10 suku pertamanya adalah...

5, 10, 15, 20

Diket :
a = 5
beda = 5

Dit = S10?

U10 = a+(n-1) b
=5 + (10-1) 5
=5 + 9.5
=5 + 45
=50

S5 = 10/2 (a+Un)
=10/2 (5+ 50)
=10/2 x 55
=5 x 55
=275