A series is defined by 5+9+13+17++805 a. Find the number of terms of the series. b. Find the sum of the first 20 terms.

the number of terms of the series is 201 numbers

              the sum of the first 20 terms is 890    

the number of terms of the series is

the series have:

u1 = 5

d = 4

=> u(n) = 5 + 4.(n - 1)

=> u(20) = 5 + 19.4 = 81

so the sum of the first 20 terms is (81 + 5).20/2 = 890

( u1 is the first number of the series, d is the  distance between front and rear numbers, u(n) is the overall term of the sequence, u(20) is the 20th of the series)

Step-by-step explanation:

answer: for each 3 girls there is 2 boys . 3: 2

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step-by-step explanation: