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This is a good question which tests you on your knowledge of divisibility rules. It also tests your understanding of the fundamental rules of Data Sufficiency.
A number will be divisible by 9 if the sum of its digits is divisible by 9. For example, 54 is divisible by 9 because the sum of its digits is 9, which IS divisible by 9. On the other hand, 137 is not divisible by 9, because the sum of its digits is 11, which is NOT divisible by 9. Hope this is clear.
Let’s look at the question now.
We can assume the three digit positive integer as xyz. When we do so, it’s clear that we are trying to find the value of y, which is the tens’ digit of the number xyz. Also, note that the biggest value that any of the digits can take is 9, while the smallest value for x is 1 (since it cannot be ZERO) and the corresponding value for y and z is 1.
Let’s analyse the statements now.
Using Statement I alone, we know that integer has to be divisible by 9. This means that the sum of the digits should be divisible by 9, i.e. x + y + z = (Multiple of 9). As can be seen, this equation can be solved in more than one ways.
For example xyz can be 126 or 999 and in both cases, xyz will be a multiple of 9.
Hence, this is insufficient.
Using Statement II alone, we know x= 9z. This can only be satisfied by one set of values viz z=1 and x = 9. However, we do not have any information on the value of y.
For example, the number can be 911 or 921 or 931 and so on till 991.
Hence, this is insufficient.
Combining the data given in both statements, we can conclude the following:
• The number has to start with 9 and end with 1.
• It has to be a multiple of 9. Hence, the sum of the digits has to be a multiple of 9.
Therefore, the only value of ‘y’ that satisfies all the above conditions is 8. So, the number is 981 and hence, the ten’s digit is 8.
This is sufficient.
So, the correct answer option is C.
In a question like this, it is very easy to subconsciously use the data given in Statement I, when trying to solve the question using Statement II alone. So option B is actually a trap answer. So, be very careful when you are analyzing the individual statements.
Hope this helps!
Arvind,
CrackVerbal Prep Team