If input is sine wave and you have an ADC fast enough, you can sample the input signal to establish the current phase - that allows you to make much smaller adjustments to the output frequency, to make the output produce exactly 10 times the number of cycles. If all you have to work with are pulses, then you can already have emitted 7 output pulses when you get the next input pulse - this resulting in 3 output pulses lost. Or what do you do when you have already reached 10 output pulses but don't see any new input pulse?

As previously noted, it's really important that you jot down all requirements you have. How much drift, jitter etc you may allow.