Question

HALP PLS 1000 students are arranged in several rows (more than 16). The numbers of students in each row are consecutive positive integers. How many students are there in the first row? (A) 20 (B) 25 (C) 28 (D) 44 (E) 80

Answer 1

Answer:

The correct option is;

(C) 28

Step-by-step explanation:

The information given are that;

The total number of students = 1000

The number of students in each row are consecutive positive numbers

Let the number of students in the first row be x,

Let the number of rows be 17

We have;

The number of students in  the last row = x + 16

The number of students in  the penultimate row = x + 15, we continue  to get;

n×x + n/2×(n-1) = 1000

(The term n/2×(n-1) is from the sum of an arithmetic progression formula)

Which gives;

17×x + 17/2×16 = 1000

17×x = 1000 - 17/2×16 = 1000 - 136 = 864

x = 864/17 = Which is not an integer,

We continue checking till we get to 25 rows which gives;

25×x + 25/2×24 = 1000

25×x + 300 = 1000

25×x  = 1000 - 300 = 700

x = 700/25 = 28

The number of student in the first row = 28 students.