Accuracy
Write each of the following numbers correct to 3 significant figures:
a) 47316.
b) 303971.
c) 20.453.
d) 0.004368.
a) 47300.
b) 304000.
c) 20.5.
d) 0.00437.
Tia and John collect marbles.
Tia has collected 335 and John has collected 442 marbles.
Choose a better estimate to find the number of marbles they own together.
To get an estimate of the sum, round off all the numbers to the same place value, then add them.
Number of marbles Tia has collected = 335 rounded off to 340
Number of marbles John has collected = 442 rounded off to 440
∴ Total number of marbles = 340 + 440 = 780
A refrigerator sells for 1024 USD. On Monday's, there's a 25% discount. Calculate the final price and amount that has been taken off the original.
Final price = 125/100 × 1024 = 768 USD
Amount decreased = 25/100 × 1024 = 256 USD
The interval on the number line below shows all the possible real lengths of the envelope.
[Illustration on the whiteboard]
Write down the correct numbers for the lower and upper limits of the interval, represented on the diagram by A and B.
A = 20.5.
B = 21.5.
a) 0.3741 to 2 d.p.
b) 3.8451 to 2 d.p.
c) 142.8315 to 1 d.p.
d) 0.000851 to 4 d.p.
a) 0.37.
b) 3.85.
c) 142.8.
d) 0.0009.
Ron is planning a major yard renovation.
He wants to reseed his entire lawn.
The shape of the yard is a rectangle.
Help Ron find the estimate of the area of his yard.
Length = 12.3ft
Breadth = 14.5ft
The dimensions of the yard are 12.3 ft and 14.5 ft.
The rounded off dimensions will be 12 ft and 15 ft.
The yard is in the form of a rectangle.
Area of rectangle = Length × Breadth
Area of rectangle = 12ft × 15ft = 180sq.ft
∴ 180 sq.ft is the required estimate.
The price of a pencil case is originally 350 UYU but on Black Friday it will cost 220 UYU. Find the percentage decrease/increase.
220/350 × 100 = 63%
The length of a card is 20.5 cm to the nearest tenth of a cm.
[Illustration on the whiteboard]
The interval on the number line below shows all the possible real lengths of the card. Write down the numbers represented on the number line by C, D and E.
[Illustration on the whiteboard]
0.1/2 = 0.05
C = 20.5 - 0.05 = 20.45.
D = 20.5.
E = 20.5 + 0.05 = 20.55.
Round each of the following numbers to the nearest 100:
a) 108.
b) 199.
c) 3471.
a) 100.
b) 200.
c) 3500.
Estimate the value of the following sum by first rounding each value to the nearest hundredth:
123.616283 + 5.123 + 6.183478
123.62 + 5.12 + 6.18 = 134.92
The starting price of apples is $150 UYU, due to inflation, the price is increased by 15%. Calculate the size of the increase.
15/100 × 150 = $22.5 UYU
Can you be sure the card will fit in the open envelope like this? Explain why.
[Illustration on the whiteboard]
The card might not fit inside the envelope, as the smallest possible length of the envelope is 20.5 cm, which is less than the largest possible length of the card, which is 20.55 cm.