If the average of a, a + 3, a + 6, a + 9 and a + 12 is 10, then a is equal to-

Question: If the average of a, a + 3, a + 6, a + 9 and a + 12 is 10, then a is equal to-

Solution:
দেওয়া আছে,
সংখ্যাগুলো হলো যথাক্রমে,
a, a + 3, a + 6, a + 9, a + 12
এবং গড় = 10

∴ সংখ্যাগুলোর যোগফল = a + (a + 3) + (a + 6) + (a + 9) + (a + 12)
= 5a + 30

সুতরাং, (5a + 30)/5 = 10
⇒ 5a + 30 = 50
⇒ 5a = 50 - 30
⇒ 5a = 20
⇒ a = 20/5
∴ a = 4

∴ সঠিক উত্তর: ঘ) 4