Let largest number is P and any two choosen numbers x and y. According to the question P + x- y is divisible by 10. So, P + x - y ≥ 10 ... (i) P is largest then x - y< P (ii) These inequalities can be written in equation form P + x - y = 10 ...(iii) and x - y = P ... (iv) On subtracting &q.(iv) by (iii), we get P+ x- y - x+ y = 10 - P P = 10-P =>2P = 10 ⇒ P =