Divide 80 Xiaofeng Xiaoyu Xiaoming is the best friend in the kindergarten. Xiaofeng weighs 14kg, which is 7 / 8 of Xiaoming's weight. Xiaoming weighs 1 / 15 of Xiaoyu's weight. How many kg should Xiaoyu weigh For a road, 3 / 8 of it was built on the first day, 6 / 7 of it was built on the second day, and 221m was left. How long is the road? These are two questions~

Divide 80 Xiaofeng Xiaoyu Xiaoming is the best friend in the kindergarten. Xiaofeng weighs 14kg, which is 7 / 8 of Xiaoming's weight. Xiaoming weighs 1 / 15 of Xiaoyu's weight. How many kg should Xiaoyu weigh For a road, 3 / 8 of it was built on the first day, 6 / 7 of it was built on the second day, and 221m was left. How long is the road? These are two questions~

Xiaoming's weight is 14 △ 7 / 8 = 16 kg - > take Xiaoming's weight as unit 1
The weight of Xiaoyu is 16 ÷ (1 + 1 / 15) = 15kg - > the weight of Xiaoyu is 1
On the first day, 3 / 8 of the road was built, on the second day, 3 / 8 × 6 / 7 = 9 / 28, and the remaining 1-3 / 8-9 / 28 = 17 / 56
Therefore, the length of this road is 221 △ 17 / 56 = 728 km