Basics of Financial Laws

Mrs. Gartenhaus borrowed 100 NIS from Mrs. Horowitz but the cab driver says he only received 20 NIS. How much does Mrs. G owe Mrs. H?

I used a local medicine gemach, which prefers receiving replacement medicine but also allows giving back with money. The pills they gave me were slightly past expiration. Isn’t it ribbit to give back either (new) pills or their monetary value, considering that expired medicine is worth less than normal?

Borrowing without the owner’s knowledge is usually halachically equivalent to stealing! In general, one may not use an item until one receives permission from the owner.