TalentJR apps
Adding 1 + 2 + 3 + … + 100 one by one takes ages. A young genius can do it in seconds: pair the first and last numbers (1 + 100), the second and second-last (2 + 99) — every pair makes 101, and there are 50 pairs.
✓ You passed this trick’s test.
Pairs — “1 + 2 + … + n = n × (n + 1) ÷ 2”
Use it for: Adding long lists, counting handshakes or cricket balls in a series, and Olympiad puzzles.
Check: 100 × 101 = 10100, and half of 10100 = 5050 ✓
Work it out in your head or on paper, type the answer and press Check. Stuck? Press “Show me how”.
Right: 0 · Tried: 0
20 questions. Check each answer, then go to the next one. Get 16 or more right to pass.
🏅 Sign in with Google to earn the ⭐ Young Genius Adder badge when you pass — and a certificate when you finish all 5 tricks of Part 2 · Number magic. You can still take the test without signing in.
Why does it work? When should you use it? Ask in English, मराठी or हिंदी.
Sign in with Google to ask Free — 20 questions a day.
Prefer a real teacher? TalentJR teachers take live online classes anywhere in India and visit homes in selected cities. Tell us what you need and our team will call you with timings and fees.