Answer:
![h = 1.75 m](https://img.qammunity.org/2020/formulas/physics/high-school/54siwfh04hkbzlvif5fdq2gz7effrs6lv4.png)
Step-by-step explanation:
As we know that height of the slide is given as
![h = 1.80 m](https://img.qammunity.org/2020/formulas/physics/high-school/ps98mk1qr97c1vtodtya8kjetwhp5kzara.png)
so time taken by the child to hit the water from the slide is given as
![t = \sqrt{(2h)/(g)}](https://img.qammunity.org/2020/formulas/physics/middle-school/en2rbn9i95dhpa4i78s5vjuts31a8eqpkq.png)
now we will plug all data in it
![t = \sqrt{(2(1.80))/(9.81)}](https://img.qammunity.org/2020/formulas/physics/high-school/yuvl6p11b3yngjosowd45w6y38wor2f8pu.png)
![t = 0.605 s](https://img.qammunity.org/2020/formulas/physics/high-school/96cbs2djffd7zx1nwck38s2f50bw0r9ivg.png)
now we know that the horizontal distance moved by it is given as
![L = v_x t](https://img.qammunity.org/2020/formulas/physics/high-school/fot06zujoloe3528u04nmeje7f7yrq8rks.png)
![3.55 = 0.605 v_x](https://img.qammunity.org/2020/formulas/physics/high-school/e1l3abde5uhedki54wwt6ucl00t9g17cc7.png)
![v_x = 5.86 m/s](https://img.qammunity.org/2020/formulas/physics/high-school/j26d1eo19gb38w3i1v8nikn7frm2pqx9si.png)
now by energy conservation
![mgh = (1)/(2)mv^2](https://img.qammunity.org/2020/formulas/physics/middle-school/1ek6f4hakzlj6dy109xhmxtx4n4wjp2p73.png)
so height of point A is given as
![h = (v_x^2)/(2g)](https://img.qammunity.org/2020/formulas/physics/high-school/m4ntyp6a7vmcavu9lexa2hhwc4ztmvnm1f.png)
![h = (5.86^2)/(2(9.81))](https://img.qammunity.org/2020/formulas/physics/high-school/wbvmlhj7fc2e9q1l6xyx1j6cn86cyt46y8.png)
![h = 1.75 m](https://img.qammunity.org/2020/formulas/physics/high-school/54siwfh04hkbzlvif5fdq2gz7effrs6lv4.png)