turkey-yks 2015 Q15

turkey-yks · Other · ygs Differential equations Qualitative Analysis of DE Solutions

A function f defined on the set of natural numbers is defined for every n as
$$f ( n ) = \begin{cases} 5 n + 40 , & 0 \leq n < 10 \\ f ( n - 10 ) , & n \geq 10 \end{cases}$$
Example: $f ( 23 ) = f ( 13 ) = f ( 3 ) = 5 \cdot 3 + 40 = 55$
Accordingly, what is the sum of the two-digit numbers AB that satisfy the equation $f ( A B ) = A B$?
A) 75 B) 80 C) 90 D) 100 E) 105

A function f defined on the set of natural numbers is defined for every n as

$$f ( n ) = \begin{cases} 5 n + 40 , & 0 \leq n < 10 \\ f ( n - 10 ) , & n \geq 10 \end{cases}$$

Example: $f ( 23 ) = f ( 13 ) = f ( 3 ) = 5 \cdot 3 + 40 = 55$

Accordingly, what is the sum of the two-digit numbers AB that satisfy the equation $f ( A B ) = A B$?

A) 75
B) 80
C) 90
D) 100
E) 105

Paper Questions

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