jika nilai rata ratanya 6 maka nilai a adalah?

Rata-rata = jumlah data / banyak data

6 = [(4×20)+(5×40)+(6×70)+(8×a)+(10×10)] / (20+40+70+a+10)
6 = (80+200+420+8a+100) / (140+a)
6 = (800+8a) / (140+a)
800 + 8a = 840 + 6a
8a – 6a = 840 – 800
2a = 40
a = 40/2
a = 20

Jawaban D