14.数理推算（14. mathematical deduction）.docVIP

14.数理推算（14. mathematical deduction） 1. there are 50 students attending the meeting, the first meeting of the female students with second boys all shook hands, the girls just boys did not hold hands, the third girls only 2 boys have shaken hands, and so on, the last one to the girl with 7 boys shook hands. Ask how many boys are there in these students? 2. of the earths total land area equivalent to 41% of the total area of the sea, the northern hemisphere land area equivalent to the sea area of 65% ______%, then, the land area of the southern hemisphere is equivalent to the ocean area (accurate to single digits). 3. a wooden box with white table tennis and yellow table tennis. Xiaoming once pulled out 5 yellow balls and 3 white balls, so N times, the white ball finished, yellow ball with 8; if a method: every time out 7 yellow ball, 3 ball, so M times, yellow ball finished, white ball left 24. How many ping-pong balls were there in the wooden box? (264) 4. a S is a natural number, divided by 10, the remainder is 9, divided by 9, the remainder is 8, by 8, the remainder is 7, and the number 100 is known as S 1000. How many are there, please? A.5 B.4 C.3 D.2 5., there are 35 students in each class, each of whom takes part in at least one extracurricular activity group in the English, language, and math groups. It is known that there are 17 people in the English language group, 30 in the language group and 13 in the math group. If there were 5 students and three groups, all of them asked how many students took part in a group A.15 people, B.16 people, C.17 people, D.18 people 6.5, 6, 6, 9, (), 90 A.12 B.15 C.18 D.21 7.2, 90, 46, 68, 57, () A.65 B.62.5 C.63 D.62 8.20, 26, 35, 50, 71, () A.95 B.104 C.100 D.102 9.4, 11, 30, 67, () A.126 B.127 C.128 D.129 Answer： 1.28 boys explained: set girls have X people, boys for Y, then the first X girls and X-1 boys did not shake hands, equal to Y-7 So theres X-1=Y-7, and theres X+Y=50 2.23% explain 65/165*1/2+1/2*X/ (100+X) =41/141*1