EXERCISES AND PROBLEMS

PRACTICE, PRACTICE, PRACTICE

32 Copy and complete the table in your notebook.

2. 7 ! 5. 29 # 4.6 51 # a) 8.73 : 1.7 – 3.42 : 2.1 b) (8.73 : 1.7 – 3.42) : 2.1 a) What can you say about the error in estimating Abel’s weight at 54.5 kilos? b) What if you estimate his weight at 54 kilos and 450 grams? a) 5 - 1 - 0.2 - 0.04 - … b) 0.24 - 1.2 - 6 - 30 - …

33 Using a calculator, round off to the nearest hundredths.

34 Amaya weighs 54 kg and 400 g. Ana weighs 54.5 kg. Abel weighs more than Amaya, but less than Ana.

35 Continue each sequence with three more terms.

36 Copy and complete this magic square in your notebook.

The sum of the numbers in each row, column and diagonal must be the same.

37 Calculate with pen and paper using the algorithm. Then, check your answer with a calculator a) , 524 b) 12 c) 73, 96 a) The product of a decimal number multiplied by an integer is always a decimal. b) Dividing two decimal numbers never gives an integer result. c) The square root of a decimal number is always less than the number. d) The square root of a decimal number is never a terminating decimal. a) 6 : 0.2 b) 15 : 0.2 c) 45 : 0.2 d) 9 : 0.3 e) 12 : 0.3 f ) 33 : 0.3 g) 6 : 0.6 h) 18 : 0.6 i ) 45 : 0.6 a) 6 5 of an hour b) 12 3 of an hour c) 5 4 of an hour a) Take the hours of sleep during their lifetime as the unit and express the portion of sleep during the first year in decimal and fractional form. b) Represent this on a number line.

38 True or false?

39 To divide by 0.2 we can multiply by ten and divide by two. Check the answer.

• 8 : 0.2 = 40 ↔ 8 · 10 = 80 → 80 : 2 = 40 Calculate mentally.

40 How many minutes are there in..?

41 Copy and complete with irreducible fractions.

42 Copy this table and complete the empty boxes following the logic of the data shown.

43 Studies show that a person sleeps some 250 000 hours in their lifetime, around 5 000 hours of which are in their first year.

Can you use this one?

Solve Simple Problems

44 Each of the 30 students in a class plays one of the following sports. Look at the graph:

Football Basketball

Volleyball

Athletics

Swimming

Dance

Which fraction of the class… a) … play football? b) … play basketball? c) … do not play basketball? d) … do not play football or basketball?

45 To produce 3 500 doses of a certain medicine, we need 1.96 kg of the active ingredient.

How many grams of this ingredient is contained in each dose?

46 How much do two kilos and eight hundred grams of apples cost at €1.65 a kilo?

47 How much will I pay if I buy 1.083 kg of salmon at €9.75/kg?

Take care when rounding off.

48 A watermelon that weighs 2 kilos and 625 grams costs €4.20. What is the price per kilo?

49 Rosa buys three quarters of a kilo of cherries at €2.80/kg and 2.25 kg of apples at €1.40/kg.

How much will she pay in total?

50 Karla bought 340 grams of ham and paid with a €10 note. She received €3.88 in change. How much is a kilo of ham?

51 A film has a duration of 1h 53 min 23 s, but with advert breaks it lasts 2 h 12 min 15 s.

What was the total duration of the advert break?

52 To celebrate a party, thirteen friends buy:

Party

✓ 6 bottles of cola at €1.65 a bottle.

✓ 1.120 kg of ham at €27.75/kg.

✓ 5 loaves of bread at €0.85 a loaf.

✓ 350 g of peanuts at €9.60/kg.

✓ 0.8 kg of crisps at €5.80/kg.

How much should each friend pay?

53 At 18 h 45 min 13 s a radio station starts broadcasting a pre-recorded music programme with a duration of 1 h 16 min 52 s. What time will the programme finish?

54 Marcelo buys a melon that weighs two kilos and four hundred grams. If the melon is sold at €1.99/kg, which of the following amounts will he pay?

55 A spinner is divided into 27 equal sections where the needle can land.

What angle does each section cover? 56 The barrel of a telescope has rotated clockwise from its initial position (North), and it is now at an angle of 158° 53' 20". What angle would it have to rotate anticlockwise from its initial position to reach the same point?

57 A van transports 250 dozen eggs which cost €0.98 a dozen. While the van is going around a curve, a box falls off and 60 eggs get broken. How much will they have to increase the price of a dozen eggs to make the same profit?

58 A tank containing 600 litres of water is two thirds full. How long would it take to fill it using a tap with a flow rate of 2.25 litres per minute?