A pupil's marks were wrongly entered as 63 instead of 43. Due to that the average marks for the class got increased by half. The number of pupils in the class is

প্রশ্ন: A pupil's marks were wrongly entered as 63 instead of 43. Due to that the average marks for the class got increased by half. The number of pupils in the class is

সমাধান:
ধরি, মোট ছাত্র সংখ্যা x
একজন বাদে বাকি ছাত্রদের নম্বরের সমষ্টি y

(y + 63)/ x = a + 0.5 ....(Ⅰ)
(y + 43)/ x = a.........( Ⅱ)

(Ⅰ) - ( Ⅱ) থেকে পাই,
{(y + 63)/ x} - {(y + 43)/ x } = a + 0.5 - a
⇒ (y + 63 - y - 43)/x = 0.5
⇒ 20/x = 0.5
⇒ x = 40

∴ ক্লাসে ছাত্র সংখ্যা ৪০ জন।