If 17th March falls on 4th day after tomorrow which is Thursday, then what day of week will fall on the last date of the month?

The problem says "tomorrow is Thursday".

Let's count what "4th day after tomorrow" means:

• Tomorrow $=$ Thursday
• 1st day after tomorrow $=$ Friday
• 2nd day after tomorrow $=$ Saturday
• 3rd day after tomorrow $=$ Sunday
• 4th day after tomorrow $=$ Monday

Therefore, 17th March $=$ Monday

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We need to find what day 31st March falls on.

Days between 17th and 31st:

$31 - 17 = 14 \text{ days}$

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Every $7$ days $=$ 1 complete week $=$ same day repeats

$14 \div 7 = 2 \text{ complete weeks}$

After 2 complete weeks, we land on the same day.

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Let's verify:

• 17th March $=$ Monday
• $17 + 7 = 24$th March $=$ Monday
• $24 + 7 = 31$st March $=$ Monday

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31st March falls on Monday