You had it right the first time, 1.7x speed is 70% faster. If something previously took 4s now takes 2s then it's 100% faster. Think of driving 10miles. If yo

You had it right the first time, 1.7x speed is 70% faster. If something previously took 4s now takes 2s then it's 100% faster. Think of driving 10miles. If you drive at 20mph then it takes 30 minutes. If you drive twice as fast, 40mph, it takes 15 minutes. 40mph is 100% faster than 20mph. Half the time is twice as fast!