Q296
If a = 4011 and b = 3989, then value of ab = ?
A.
15999879
AnswerB.
15899879
C.
15989979
D.
15998879
Answer: Option A
Solution
Answer: Option A
Solution:
a = 4011b = 3989
a × b = 4011 × 3989
= 15999879
Shortcut method :
a = 4011 ⇒ (4000 + 11)
b = 3989 ⇒ (4000 - 11)
[(a - b) (a + b) = a2 - b2]
According to the question,
a × b = (4000 + 11) (4000 - 11)
= 40002 -112
= 16000000 - 121
= 15999879