Linsha

If the chairs in an auditorium are arranged in an arithmetic sequence 5 th row contains 31 chair and 16 th row contains 75 chairs then find the total number of chairs if there exists 20 rows

The common difference of an arithmetic sequence is d prove that the sum of first n terms and next n terms differ by n×n×d

The angles of a cyclic quadrilateral are the consecutive terms of arithmetic sequence and one of the angle is 45(degree) What are the measures of other 3 angles

16-5=11, 75-31=44 d=4 First term = 4d-31 = 4×4-31 = -15 Number of chairs if there exists 20 rows =n÷2(2f+(n-1)d) =20÷2(2×(-15)+(20-1)4) =460

x+3x=180 4x =180 x =180÷4 x =45 First angle = 45 Third angle = 3×45 = 135

1x+3x+5x= 180 9x = 180 x =180÷9 = 20 5×20=100 100 is the measurement of largest angle

1.A 2.B