YOU SAID:

it's like complaining that cars are useless because they can barely go 1/5 of the speed of airplanes

INTO JAPANESE

彼らはほとんど飛行機の1/5の速度で行けないので車は無用であると不平を言うようです

BACK INTO ENGLISH

They seem to complain that cars are useless because they can hardly go at 1/5 the speed of the plane

INTO JAPANESE

彼らは飛行機の1/5の速度ではほとんど行けないので車は役に立たないと文句を言っているようです。

BACK INTO ENGLISH

They seem to complain that they are not useful because they can hardly go at 1/5 the speed of the plane.

INTO JAPANESE

彼らは、飛行機の1/5の速度では行けないので、役に立たないと文句を言っているようです。

BACK INTO ENGLISH

They seem to complain that they are not useful because they can not go at 1/5 the speed of the plane.

INTO JAPANESE

彼らは飛行機の1/5の速度では行けないので役に立たないと不平を言うようです。

BACK INTO ENGLISH

They seem to complain that they are not useful because they can not go at 1/5 the speed of the plane.