Question

Consider the following sum :

•+1 • 1+ 2 • + • 3+ • 1 = 21 •

In the above sum, • stands for

(a) 4
(b) 5
(c) 6
(d) 8

Answer 1

option d is the answer...........

Answer 2

Answer:

8

d is correct.

Step-by-step explanation:

Given: • + 1 • + 2 • + • 3 + • 1 = 21 •

using base 10 system to solve this.

There are five terms to add. First we write each term in expanded form.

Tens place show multiply by 10.

For example: xy  where, x is tens place and y ones place.

xy = 10x + y

Let • be n

Replace •  with n from equation.

• + 1 • + 2 • + • 3 + • 1 = 21 •

n + 1n + 2n + n3 + n1 = 21n

Expand each term using base ten system.

n + 10 + n + 20 + n + 10n + 3 + 10n + 1 = 210 + n

                                              23n + 34 = 210 + n

                                                      22n = 176

                                                           n = 8

If • replace with 8 then get true result.

Hence, The  •  (dot) stands digit 8