(1) Administrative test-Quantity relationship

1, 1999 of the 1998-digit number of the square is ()

A. 1 B. 3 c. 7 D. 9

The mantissa formula: 1~9 The last number of their own by themselves are four a cycle.

The 1-exponent mantissa is the 1, 1, 1, 1 loops

The 2-exponent mantissa is the 2, 4, 8, 6 loops

The 3-exponent mantissa is the 3, 9, 7, 1 loops

The 4-exponent mantissa is the 4, 6, 4, 6 loops

The 5-exponent mantissa is the 5, 5, 5, 5 loops

The 6-exponent mantissa is the 6, 6, 6, 6 loops

The 7-exponent Mantissa is the 7, 9, 3, 1 loops

The 8-exponent mantissa is the 8, 4, 2, 6 loops

The 9-exponent Mantissa is the 9, 1, 9, 1 loops

So the exponent 1998 divided by 4 equals 499 to 2.

When there is no remainder, it is the fourth number of the loop, and the remaining 2 must be the number of two numbers in the future, which is the 2nd number of the loop. Because the base is 9, the answer is a.

2 Split Phase Elimination formula

(1) Administrative test-Quantity relationship