please Jawab no 1 belom ngerti nih pake caranya ya

jawab

Kecepatan rata rata = 

=  { 15 x 10 + 30 x 20 + 40 x  30 + 60 x 40 + 75 x50 }/ (15+30+40+60+75)

= (150+600+1200+2400+3.750) / (220)
= 8.100 /220
= 36,8