You started out with 260, and increased to 430.
The amount you increased was (430 - 260) = 170
170 is (170/260) = 65.4% of what you started with.
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Another way:
The new amount is (430/260) of the old amount.
430 / 260 = 1.654 = 165.4%
The original amount was 260.
You started with 100% of it.
You ended up with 165.4% of it.
That's an increase of 65.4% .
