Slash Brain Boosters
Memory palace, Stroop test, digit span - playable brain training plus daily drills.
🎮 Playable brain games
Brain Teaser Vault
20 classics with answers - searchable.
A bat and ball cost ₹1.10 together. The bat costs ₹1 more than the ball. Ball?
→ 5 paise. (Not 10 - that's the intuitive trap.)
5 machines make 5 widgets in 5 minutes. How long do 100 machines take for 100 widgets?
→ 5 minutes.
Lily pads double daily and fill the lake in 48 days. When is it half full?
→ Day 47.
You have two ropes that each burn for exactly 60 min but unevenly. Measure 45 minutes.
→ Light rope A at both ends and rope B at one end. When A finishes (30 min), light B's other end (15 more).
What comes once in a minute, twice in a moment, but never in a thousand years?
→ The letter M.
A man looks at a painting and says 'brothers and sisters I have none, but that man's father is my father's son.' Who is in the painting?
→ His son.
Three switches, one bulb upstairs. You may go up once. Identify the right switch.
→ Turn switch 1 on for 10 min, off; switch 2 on; go up. Lit = 2, warm-off = 1, cold-off = 3.
Two coins add to 30 paise; one is not a 20-paise coin. What are they?
→ 20 and 10 - the other one is the 20.
You're in a race and overtake second place. What place are you in?
→ Second. (Not first.)
A farmer needs to cross a river with a wolf, a goat and cabbage; boat fits him + one. Wolf eats goat, goat eats cabbage. Order?
→ Goat over; back; wolf over, goat back; cabbage over; goat over.
Which weighs more: a kilo of feathers or a kilo of steel?
→ Equal. The trap is units, not weight.
A clock shows 3:15. What is the angle between the hands?
→ 7.5 degrees.
Numbers That Sound Fake
Real magnitudes, for perspective.
8,000,000,000
humans alive right now — you could give each one a unique 33-bit ID
4,000,000 tonnes
of mass the Sun fuses into energy every single second
1.4 billion
photos are taken globally per day — about 16,000 every second
95%
of the ocean remains unmapped and unexplored in detail
100,000 miles
of blood vessels inside one human body — 4× around the Earth
43 quintillion
possible Rubik's Cube positions — more than grains of sand on Earth
300 billion
stars in the Milky Way, and 2 trillion galaxies observable
0.0000001%
of the universe's volume is occupied by ordinary matter
Memory Chain
Random 7-item chain — memorise it, then check yourself tomorrow.
N-Back Trainer
Say each letter aloud, two positions back. Brutal, effective.