Starting on the circled date, Mohan waters his mango saplings every 9 days. On which day of the week is the 10th watering?

The 10th watering is 9 intervals after the first: $9\times 9=81$ days later. 81 = 11 weeks + 4 days, so Sunday + 4 = Thursday (it is 24 May). (Saturday uses $10\times 9=90$ days; Tuesday counts only 8 gaps.)