The phrase "reduced to a third" is correct and usable in written English.
It can be used when talking about a reduction of a quantity to one-third of the original amount. For example, "The number of people attending the event had been reduced to a third of the original amount due to the bad weather."
Let it bubble away until the mixture is reduced to a third, which will take 10 15 minutes.
He said haemophilia medicines available in Iranian markets had been reduced to a third of former supply levels.
Bluish little phosphorous flames still flickered around many of them; others had been roasted brown or purple and reduced to a third of their normal size.
The Tigris in Baghdad is reduced to a third of its normal level, disease-ridden livestock are dying of hunger, and worse is still to come.
It consists of a set of coupled partial integro-differential equations which is reduced to a third order nonlinear coupled fluid-plate vibration equation by using the assumed mode method to approximate the plate dynamic deflection.
Its main advantage over other methods is that the corresponding characteristic equation can be reduced to a third order one, no matter how many elements are discretized in calculation.
Nayfeh, Perturbation Methods, Wiley-Interscience, New York, 1973], the original non-autonomous system is reduced to a third-order approximate autonomous system.
With each diving catch, with every reception underneath followed by one deep downfield, it was as if Chrebet were refuting the speculation that he could be reduced to a third-down specialist.
The prospect of being discredited, "reduced to a second-rate power," was what drove the war forward.
It was not runaway trains but a fear of being humbled, "reduced to a second-rate power," that drove the war forward.
For example, the second figure syllogism can be reduced to a first figure syllogism by simply converting the first premise to the equivalent "No B is A".
