YOU SAID:

my cat can leap so far that I think he could cross the river

INTO JAPANESE

私の猫は川を渡ることができると思うほど飛躍することができます

BACK INTO ENGLISH

My cat can leap as much as I think can cross the river

INTO JAPANESE

私の猫は川を渡ることができると思う限り跳躍することができます

BACK INTO ENGLISH

My cat can jump as long as he thinks he can cross the river

INTO JAPANESE

私の猫は川を渡れると思っている限りジャンプできます

BACK INTO ENGLISH

My cat can jump as long as he thinks he can cross the river