Question

Rumus jumlah bilangan kelipatan 5 antara 200 dan 400

Answer 1

Kelipata 5 antara 200 – 400 
u1 = a = 205
b = 5
Un = 395
jawabnnya
Un =a + (n-1)b
395= 205 + (n-1)5
395 = 205 + 5n – 5
395 = 200 + 5n
395-200= 5n
195 = 5n
195/5 = n
   39 = n
Sn = n/2 (2a + (n-1)b )
S49 = 39/2 (2 x 205 + ( 39-1)5)
        = 39/2 ( 410 + 190 )
         = 39/2 x 600
         = 39 x 300 
         = 11700

jawabnnya 11700

Answer 2

200 + 5 = 205
400 - 5 = 395

395 - 205 = 190 : 5
                  = 38 + 1 = 39

39 / 2 x (2 x 205 + (39-1)/5
39/2  x 600
= 11.700