Question
A shopkeeper give 4 articles free on the purchase of
every 12 articles. He also allows a discount of 20% to customer and still earns 20% profit. Find the ratio of cost price to mark price of the article.Solution
Buy 12 get 4 free,% discount offered = [4/(12 + 4)] ×100 = 4/16×100 = 100/4 = 25% So final Offer(discount) = Buy 12 get 4 free + 20% discount = 25% discount +20% discount So net discount = a + b - ab/100 = 25 +20 – (25 × 20/100) = 45 – 5 = 40% Let MP = 100 SP = (100-40% discount on MRP ) = 100 -40 = 60 Profit = 20% = 1/5 So CP = 50 CP∶ MP = 50∶ 100 = 1∶ 2 Alternate Method 
612, 487,?, 396, 388, 387
Find the missing number in the given number series.
1, 2, 6, 24, 120, ?What will come in place of the question mark (?) in the following series?
36, 85, ?, 230, 330, 451
Find the missing term in the series:
2, 5, 11, 23, 47, ?
What will come in place of the question mark (?) in the following series?
400, 841, 1202, ?, 1716, 1885
44   45    41   50    ?      59    23
...221, 100, 0, -81, ?
...900 Â Â Â 90Â Â Â 18Â Â Â ? Â Â Â Â 2.16Â Â Â Â 1.08
16, 20, 11, 27, ?, 38
37, 57, 82, ?, 147, 187
