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Problematics | How to multiply, and why it works
This week, we try a different multiplication method and a puzzle including substitution and addition. Good luck!
The way we multiply is something we take for granted, but at least we know why the method works: why, that is, we start from the right and why we carry over digits from one column to the next one on the left. Imagine how difficult multiplication would have been if we didn’t use the decimal system.
How did people multiply numbers in the days before the decimal system? Different civilisations would have had different methods, one of which we will look at today. Our modern method is more efficient, of course, but the following procedure (originally Russian, I think) is quite smart by any standard.
# Puzzle 35.2: Hello Sir, If a gambler wins and loses an equal number of bets, he will lose 25% of the money he begins the round with for every round of one win and one loss. If he starts with ₹100, he will stake ₹50. If he wins, he has ₹150. Now, he stakes ₹75 and loses it. So, he is left with ₹75. If he loses first and then wins, he will still have ₹75. So, he will end the games at a loss only. — Sunita Gupta, Patel Nagar, Delhi |
| The list below contains the name Sunita Gupta twice. To make it clear, these are two different solvers, both from Delhi. |
| Solved both puzzles: Rahul RB (Mumbai), Sunita Gupta (Patel Nagar, Delhi), Dr Sunita Gupta (Delhi), Rajesh Bansal (Noida), Harshit Arora (Delhi), Kanwarjit Singh (Delhi), Tosheeba Naidu (Delhi), Akshai Bakhai (Mumbai), Sanjay Gupta (Delhi), Sunita & Naresh Dhillon (Gurgaon), Shrey Gujral (Delhi), Amardeep Singh (Meerut), Shishir Gupta (Indore), Rahul Agarwal (Bay Area, California), Narendra Kumar Aggarwal, Puneet Vashistha, Om Prakash Sharma, Bhavishya Kait, Anshul Kumar, Hurditya Dand |
| Solved #Puzzle 35.1: Ananya Duggal (Indirapuram), Dinesh Gupta (Bathinda), Nipun Bamania (Mumbai), Mayobhav Pathak (Gurgaon), Priya Naidu (Delhi) |
| Solved #Puzzle 35.2: Amar Lal Miglani (Mohali), Geetansha Gera (Faridabad), Sanjeev Varghese |
