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GATE 2020 MA – Question 27

Algebra · Fields and Extensions · 1 mark · Numerical answer

A field F has 4096 elements. Find its number of proper subfields.

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Correct answer: 5 to 5

Explanation

Since $4096=2^{12}$, subfields are exactly $\mathbb F_{2^d}$ for positive divisors d of 12, with one subfield for each divisor. These divisors are 1,2,3,4,6,12. The last gives F itself and is not proper. Therefore the number of proper subfields is five.

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