Speed Maths Ch 10: Multiply by 9, 99 aur 999 (Saare Posts)

9, 99 aur 999 bas 10, 100 aur 1000 se 1 kam hain. Isliye inse guna do chhote kadam mein: number ke peeche 0, 00 ya 000 lagao (10, 100 ya 1000 se guna), phir wahi number ek baar ghatao (47 × 9 = 470 − 47 = 423). Aur jab number mein utne hi ya kam digit hon jitne 9 hain, to ek aur tez raasta: left mein number se 1 kam, right mein 10, 100 ya 1000 se baaki (47 × 99 → 46 | 53 = 4653). Chitra se samjhenge yeh kyun chalta hai, 0 se khaane bharna (99 × 99 = 9801), aur kab seedha tareeka hi behtar hai. Har post mein timer, diagram, drill, MCQs aur Challenge.