初雪小白，下面是代碼：

package main

import (
    "fmt"
)

func main() {
    var balance = []float32{1000.35, 2.3, 3.6, 17.32, 51.966, 101.12, 1023.124}
    var sum, avg float32
    var num = len(balance)
    for i := 0; i < num; i++ {
        sum += balance[i]
    }
    avg = sum / num
    fmt.Println(avg)
}

報(bào)錯(cuò)信息：invalid operation: sum / num (mismatched types float32 and int)

求大神解答 到底是哪里的問(wèn)題？