निम्न सारणी का बहुलक ज्ञात कीजिए
`{:(`वर्गान्तर`, " `आवृत्ति`),(0-10," "9),(10-20," "17),(20-30," "28),(30-40," "23),(40-50," "15),(50-60," "8):}`

Answer

`26.88`