Which number can be added to a rational number to explain that sum of two rational numbers is rational

Lems1. the following data set represents the scores on intelligence quotient(iq) examinations of 40 sixth-grade students at a particular school: 114, 122, 103, 118, 99, 105, 134, 125, 117, 106, 109, 104, 111, 127,133, 111, 117, 103, 120, 98, 100, 130, 141, 119, 128, 106, 109, 115,113, 121, 100, 130, 125, 117, 119, 113, 104, 108, 110, 102(a) present this data set in a frequency histogram.(b) which class interval contains the greatest number of data values? (c) is there a roughly equal number of data in each class interval? (d) does the histogram appear to be approximately symmetric? if so,about which interval is it approximately symmetric?

An arc subtends a central angle measuring 7pi/4 radians what fraction of the circumference is this arc?

How do i start to solve? would appreciate a walk-thru! a bird sitting 16ft above the ground in an apple tree dislodges an apple. after how many seconds does the apple land on the ground? (assuming that no branches will interfere with it's fall)