One integer A after another is added to 12.
Then integers as 12, 12 + A, 12 + A + A, -------- are coming out.
When these numbers is rounded off at ones digit, it will become at order 10, x, 40, 50, 70, y -------.
Answer to the following questions.
(1) Find A.
(2) Find the number filled in x and y.
Then integers as 12, 12 + A, 12 + A + A, -------- are coming out.
When these numbers is rounded off at ones digit, it will become at order 10, x, 40, 50, 70, y -------.
Answer to the following questions.
(1) Find A.
(2) Find the number filled in x and y.
Answer
Solution
(1) The answers of these calculation of 12 + A × 2, 12 + A × 3, 12 + A × 4 is rounded off at ones digit comes to 40, 50, 70, respectively.
It can be expressed that 35 =< 12 + A × 2 < 45, 45 =< 12 + A × 3 < 55,
65 =< 12 + A × 4 < 75.
These formulas are turned to 23 =< A × 2 < 33, 33=< A × 3 < 43, 53=< A × 4 < 63.
Furthermore, ① 11.5=< A < 16.5, ② 11=< A < 14.3---, ③ 13.25=< A < 15.75.
The integer applicable to A is ①12, 13, 14, 15, 16 ②11, 12, 13, 14, ③14, 15.
The integer included in all is 14.
(2) Since A = 14, 12 + 14 = 26.
(1) 14
(2) x = 30, y = 80
(2) x = 30, y = 80
(1) The answers of these calculation of 12 + A × 2, 12 + A × 3, 12 + A × 4 is rounded off at ones digit comes to 40, 50, 70, respectively.
It can be expressed that 35 =< 12 + A × 2 < 45, 45 =< 12 + A × 3 < 55,
65 =< 12 + A × 4 < 75.
These formulas are turned to 23 =< A × 2 < 33, 33=< A × 3 < 43, 53=< A × 4 < 63.
Furthermore, ① 11.5=< A < 16.5, ② 11=< A < 14.3---, ③ 13.25=< A < 15.75.
The integer applicable to A is ①12, 13, 14, 15, 16 ②11, 12, 13, 14, ③14, 15.
The integer included in all is 14.
(2) Since A = 14, 12 + 14 = 26.
By rounding off at ones digit, x = 30.
12 + A × 5 =12 + 14 × 5 = 82.
By rounding off at ones digit, y = 80.
