IBPS PO Prelims 23 Aug 2025 Shift 3 Solved Paper

Concept:The average of boys and girls in a year is $\frac{\text{Boys} + \text{Girls}}{2}$, so $\text{Girls} = 2 \times \text{Average} - \text{Boys}$.Explanation:First, find the number of girls in 2004 and 2005 using the given average and boys data.For 2004: Average $= 180$, Boys $= 120$.$\text{Girls} = 2 \times 180 - 120 = 360 - 120 = 240$.For 2005: Average $= 150$, Boys $= 200$.$\text{Girls} = 2 \times 150 - 200 = 300 - 200 = 100$.Now, total boys in 2001 and 2002 together:Boys in 2001 $= 160$, Boys in 2002 $= 200$.$\text{Total boys} = 160 + 200 = 360$.Total girls in 2004 and 2005 together:$\text{Total girls} = 240 + 100 = 340$.Required ratio $= 360 : 340$.Divide both terms by $20$: $360 \div 20 = 18$, $340 \div 20 = 17$.So, ratio $= 18 : 17$.Answer:$18 : 17$ (Option B).