Câu số 68: If a = 1; b = 5 and the average of a,b,c is 8 then c =…….. Câu số 69: There are …………even numbers from 1 to 15. Câu số 70: If 35 + x = 92 then x =…….. Câu số 72: 3m 6dm + 280cm = …………….cm Câu số 73: 3 minutes 20 seconds = …………..seconds Câu số 74: There are 9 more boys than girl in a class. There are 37 students in all. How many boys are there in the class? A – 14 B – 25 C – 23 D - 12 Câu số 75: If x = 5221 then x × 9 =………. Câu số 76: The sum of two numbers is the greatest 2 – digit number and their difference is 13. The greater number is………. A – 41 B – 43 C – 56 D – 58 Câu số 77: The perimeter of a rectangle is 36cm and its length is 6cm more than its width. Its area is …………cm2 Câu số 78: The average of 21 and 23 is ………… Câu số 79: Calculate: 6523 + 7643 × 2 =………. Câu số 80: Minh and Nam have a total of 9 pencils. If Minh has 4 pencils more than Khoa, then Nam and Khoa have a total of ……….pencils