數學題 (英文)

1)Mary got 50 marks in the first Chinese dictation . If her mark in the
second Chinese dictation increased by 20% , and her mark in the third Chinese dictation was 20% more than the second dictation , find her
mark of the third Chinese dictation.
Her second dictation mark is 50 * (1 + 20%)
= 50 * 1.2
= 60
Her third dictation mark is 60 * (1 + 20%)
= 60 * 1.2
= 72
2)The electricity bill of Mary's family on August was $560. If in the
next two consecutive months, the use of electricity is less than each
previous month by 15%, find the electricity bill of Mary's family in
October.(give the answer correct to the nearest integer.)
The electricity bill of Mary's family in September = $560 * (1 – 15%)
= $560 * 0.85
= $476
The electricity bill of Mary's family in October = $476 * (1 – 15%)
= $476 * 0.85
= $405 (correct to the nearest integer)
3)Last month, there were 30 male students and 20 female students in
the chess class. The number of male students decreases by r % and
the number of female students increases by r % in this month. If the
number of male and female students are the same in this month, find r.
The number of male students = 30 * (1 – r%)
The number of female students = 20 * (1 + r%)
30 * (1 – r%) = 20 * (1 + r%)
30 – 0.3r = 20 + 0.2r
30 – 20 = 0.2r + 0.3r
10 = 0.5r
r = 10/0.5
r = 20
4)Express the angle that the minute hand of a clock makes in 10
minutes as a round angle.
There are 60 minutes around the clock for the minute hand
10 minutes is 10/60 of a circle
One complete circle = 360 degrees
The angle that the minute hand of a clock makes in 10 minutes = 360 degree * (1/6)
= 60 degrees
5)A ribbon 176 cm long is used to wrap around a cubic gift box. Find the length of one side of the gift box.
Let one side of the gift box be x cm
Wrapping around a cubic gift box requires four times of the length of one side
4x = 176
x = 44
The length of one side of the gift box = 44cm