Mathematic Question...

1)Maximum absolute error = 0.1 s
Measured value = 21 s
Maximum relative error
= 0.1 / 21
= 1 / 210
Maximum percentage error
= Maximum relative error X 100%
= 1 / 210 X 100%
= 0.476 % (cor. to 3 sig. figs.)

2)Let x be the number of tens digit and unit digit and y be the number of hundred digit.
(100x + 10x + y) - (100y + 10x + x) = 198...(1)
x + y = 6...(2)
From (1), (100x + 10x + y) - (100y + 10x + x) = 198
100x + 10x + y - 100y - 10x - x = 198
99x - 99y = 198
x - y = 2...(3)
(1) + (3), x+y+(x-y) = 6+2
2x = 8
x = 4
Sub. x = 4 into (2),
4+y = 6
y = 2
therefore the original number is 244.

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