Revision

97,53,210

Step 1: To form the greatest number, arrange all digits in descending order (largest first). Step 2: Digits given: 3, 7, 0, 5, 9, 2, 1. Sort in descending order: 9, 7, 5, 3, 2, 1, 0. Step 3: Place them from left to right: 9-7-5-3-2-1-0. Step 4: Write with Indian comma placement: 97,53,210. Final answer: 97,53,210. Common mistake: placing 0 at the beginning or not sorting correctly, giving wrong arrangements like 97,53,201.

70,43,852

Step 1: List digits at each place — Ten Lakhs: 7, Lakhs: 0, Ten Thousands: 4, Thousands: 3, Hundreds: 8, Tens: 5, Ones: 2. Step 2: Write in order from ten lakhs to ones: 7-0-4-3-8-5-2. Step 3: Place Indian commas: after ten lakhs and lakhs group = 70, then after next two digits = 43, then last three = 852. Step 4: Number = 70,43,852. Common mistake: skipping the 0 in the lakhs place and writing 74,03,852.

20,00,000 + 7,00,000 + 6,000 + 400 + 50

Step 1: Write 27,06,450 in a place value chart — Ten Lakhs: 2, Lakhs: 7, Ten Thousands: 0, Thousands: 6, Hundreds: 4, Tens: 5, Ones: 0. Step 2: Multiply each non-zero digit by its place value: 2×10,00,000=20,00,000; 7×1,00,000=7,00,000; 0 (skip); 6×1,000=6,000; 4×100=400; 5×10=50; 0 (skip). Step 3: Expanded form = 20,00,000 + 7,00,000 + 6,000 + 400 + 50. Common mistake: confusing 6 in the thousands place with ten thousands and writing 60,000.

1

Step 1: We need to find 60,00,000 − 59,99,999. Step 2: Subtract: 60,00,000 − 59,99,999. Step 3: 60,00,000 = 59,99,999 + 1 (since adding 1 to the greatest 7-digit... wait, 59,99,999 is not the greatest 7-digit). Let us subtract directly: 60,00,000 − 59,99,999 = 1. Step 4: This confirms that 59,99,999 + 1 = 60,00,000. So 60,00,000 is just 1 more than 59,99,999. This is similar to how 10,00,000 = 9,99,999 + 1.