CAIRO EASES PRICES, BUT RIOTING GOES ON
Pres Sadat, after 2d day of widespread rioting and increasing casualties, cancels price increases for food, cooking fuel and other products; violence continues; newspaper Al Ahram repts 21 persons killed, 360 injured and 439 arrested in Cairo and Alexandria in 2 days; Egyptian authorities order curfew in Cairo, Alexandria and Suez; curfew, 1st since '52 overthrow of King Farouk, is defied, and police rept battling with demonstrators in several places; Sadat returns to Cairo from Aswan to deal with crisis; Deputy Prime Min Abdel Moneim Kaissouni, who was responsible for price increases, submits his resignation, but it is rejected by Prime Min Mamdouh Salem; Interior Min blames troubles on Communist agitators and says police will maintain order; map (L)