Hello Mun23,

The easy way to solve such questions is to divide the numbers individually by 8 and then multiply the remainders. Confirm whether the product of the remainders can be divided by 8 again. If yes, then divide and find the remainder and that will be your answer. If not, then the product of the remainders is your answer.

Here are a few examples to show this.

Find the remainder of 15*9/4. 15/4 gives a remainder of 3 and 9/4 gives a remainder of 1. Hence, the total remainder is the product of the remainders=3 which cannot be further divided BY 4. Let us confirm this the long way. 15*9=135. Divide 135 by 4 and you get a quotient of 33 and a remainder of 3.

Similarly, try 21*9/7. 21/7 gives a remainder os 0 and 9/7 gives a remainder of 2. Hence, 0*2=0 is the total remainder. You can try this the long way.

Now, coming to the question at hand 47/8 gives a reminder of 7 and 49/8 gives a remainder of 1. 7*1=7 is the total remainder and thus, the answer is e.

Hope this helps! Let me know in case of any further questions.

(47)(49)=(8X5+7)X(8X6+1)
=(8X5)X(8X6)+(8X5)X1+(8X6)X7+7X1
all other terms have 8 as a factor except 7X1 hence remainder is 7.

Is it really a 700+ question??

I have an alternate learnt here

\(Rof (47) (49)\) when divided by 8

Always reminder of product of two numbers divided by a divisor will be equal to product of reminders of corresponding numbers divided by same divisor


Using this rule,
\(Rof (47)\) = 7
\(Rof (49)\) = 1

So\(Rof (47) (49)\) = 7*1 =7

Other way would be
\(Rof (47)\) = -1 ( which is same as 7, but to do simpler we use -ve number 8-7)
\(Rof (49)\)= 1
So\(Rof (47) (49)\) = -1*1 =-1
Therefor 8-1= 7

I'm missed the link from which i learnt this..
I'm searching for it.. Once i get it will post it up here !!
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That's exactly how I solved it. I like this approach best. Kudos Sadovskiya!

\(\frac{47}{8}\) = Remainder \(7\)
\(\frac{49}{8}\) = Remainder \(9\)

\(\frac{63}{8}\) = Remainder \(7\)

Thus, answer will be (E) Remainder \(7\)
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Thanks and Regards

Abhishek....

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+E
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product of units digits=63
63/8 leaves remainder of 7
E