The 14 digits of a credit card are written in the boxes shown. If the sum of any three consecutive digits is 16, what is the value of [tex]A[/tex]?

[tex]\[
\begin{tabular}{|c|c|c|c|c|c|c|c|c|c|c|c|c|c|}
\hline
A & & 9 & & & & & & & & & 9 & & 5 \\
\hline
\end{tabular}
\][/tex]

[tex]\[
A = \square
\][/tex]



Answer :

To determine the value of [tex]\( A \)[/tex] given that the sum of any three consecutive digits in this sequence equals 16, let’s analyze the sequence step-by-step.

We are given:
[tex]\[ A \quad _ \quad 9 \quad _ \quad _ \quad _ \quad _ \quad _ \quad _ \quad _ \quad 9 \quad _ \quad 5 \][/tex]

Since the sum of any three consecutive digits is 16, we can set up the following relationships:

1. Considering the first three digits:
[tex]\[ A + \text{blank} + 9 = 16 \][/tex]

Let's denote the blank by [tex]\( x \)[/tex]:

[tex]\[ A + x + 9 = 16 \][/tex]

Solving for [tex]\( x \)[/tex]:

[tex]\[ x = 16 - A - 9 \][/tex]
[tex]\[ x = 7 - A \][/tex]

2. Consider the next three digits involving the digit 9:
[tex]\[ \text{blank} + 9 + \text{blank} = 16 \][/tex]

Denote the blanks around 9 by [tex]\( x \)[/tex] and [tex]\( y \)[/tex]:

[tex]\[ x + 9 + y = 16 \][/tex]

Substituting [tex]\( x \)[/tex] from our previous result, [tex]\( x = 7 - A \)[/tex]:

[tex]\[ (7 - A) + 9 + y = 16 \][/tex]

Solving for [tex]\( y \)[/tex]:

[tex]\[ 16 - 7 + A - 9 + y = 16 \][/tex]
[tex]\[ 7 - 16 + 7 + y = 16 - 16 \][/tex]
[tex]\[ y = A \][/tex]

3. Now, let’s consider another set of three digits that involve [tex]\( A \)[/tex]. Let’s use the consecutive 9's and the provided 5 towards the end of the sequence:
[tex]\[ \text{blank} + 9 + 9 = 16 \][/tex]
[tex]\[ x + 9 + 9 = 16 \][/tex]

Since [tex]\( x \)[/tex] earlier was represented as [tex]\( 7 - A \)[/tex]:

[tex]\[ 7 - A + 9 + 9 = 16 \][/tex]
[tex]\[ 7 + 18 - A = 16 \][/tex]
[tex]\[ 25 - A = 16 \][/tex]

Solving for [tex]\( A \)[/tex]:

[tex]\[ A = 25 - 16 \][/tex]
[tex]\[ A = 9 \][/tex]

Therefore, the value of [tex]\( A \)[/tex] is [tex]\( \boxed{9} \)[/tex].

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