Matematikadan

743. Когда из бочки взяли у имевшейся в ней
воды и еще 19 л, то в ней осталось 23 л.
Сколько литров воды было в бочке?
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744. After driving 240 km, — of a trip was com-
5
pleted. How long was the total trip?
3
745. —of a school population are boys. What frac-
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tion of the pupils are girls? If there are 164
girls, how many boys are there?
746. Tub sonlarning quyidagi xossalarini 5 - 6 ta
misolda tekshirib ko'ring:
1) 2 dan katta har qanday juft natural sonni
ikkita tub sonning yigmdisi ko‘rinishida tasvirlash
mumkin.
2) 5 dan katta har qanday toq natural sonni
uchta tub sonning yig‘indisi ko‘rinishida tasvirlash
mumkin.
747. Agar ikkita tub son ayirmasi 2 ga teng bolsa,
ular egizak tub sonlar deyiladi. Masalan, 3
va 5; 5 va 7; 17 va 19; egizak tub sonlar dir.
1) Tub sonlar jadvalidan foydalanib, 997 gacha
bolgan tub sonlar ichida egizak tub sonlar
nechtaligini hisoblang.
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val tuzing. (Egizak sonlar soni cheklimi yoki
ular cheksiz ko'pmi? degan savol ≪egizaklar
muammosi≫ nomi bilan mashhur va hamon
hal qilinmagan. Balki uni Siz hal qilarsiz?)
748. 1) Ketma-ket kelgan har qanday uchta natural
son ko‘paytmasining 6 ga bolinishini isbotlang.
(Avval misollarda sinab ко ring.)
2) Ketma-ket kelgan har qanday uchta natural
sonning birinchisi juft son bolsa, ular
ko‘paytmasining 24 ga bolinishini isbotlang.