(a) Weight of cement = 3,675 kg
Weight of steel = 2,850 kg
Total weight of cement and steel
= 3,675 kg + 2,850 kg = 6,525 kg
So, total weight loaded onto the truck = 6,525 kg
(b) Maximum capacity of truck = 8,250 kg
Weight of cement and steel loaded on the truck = 6,525 kg
Remaining weight = 8,250 kg – 6,525 kg = 1,725 kg
So, the truck can carry 1,725 kg more before reaching its maximum capacity.
NCERT Textbook Pages 51-52
Quick Sums and Differences
Sukanta likes the numbers 10, 100, 1,000, and 10,000. He wants to figure out what number he should add to a given number such that the sum is 100 or 1,000. Help him fill in the blanks with an appropriate number.
59 + _____ = 100
Try this method for the number 59.
Solution:
Now, use this method to solve the following.
877 + ________ = 1,000 and 666 + ________ = 1,000
4,103 + ________ = 10,000 and 5,555 + ________ = 10,000
Solution:
Will this method work if the units digit is 0? What do you think? What other methods can you use to find the missing number to fill in the blanks? Share your thoughts in the class.
(a) 180 + ________ = 1,000
Solution:
180 + ________ = 1,000
(b) 760 + ________ = 1,000
Solution:
760 + ________ = 1,000
(c) 400 + ________ = 1,000
Solution:
400 + ________ = 1,000
Yes, it works, even when the unit digit is 0 Other method to find the missing number.
(a) 180 + _____ = 1,000 9 10
_____ = 1,000 – 180
(b) 760 + _____ = 1,000
_____ = 1,000 – 760
(c) 400 + = 1,000 10
_____ = 1,000 – 400
Rule: To find the missing number in an addition sentence like.
Known number + _____ = Total.
We can just subtract known number from total.
Namita likes the number 9. She wants to subtract 9 or 99 from any number. Find a way to quickly subtract 9 or 99 from any number.
(a) 67 – 9 = _____
Solution:
(b) 83 – 9 = _____
Solution:
(c) 144 – 9 = _____
Solution:
(d) 187 – 99 = _____
Solution:
(e) 247 – 99 = _____
Solution:
(f) 763 – 99 = _____
Solution:
Rule: To subtract 9 or 99 from any number. Subtract 10 or 100 from the given number and add 1 in result.
Namita wonders if she can get 9 or 99 as the answer to any subtraction problem. Find a way to get the desired answer.
(a) 32 – _____ =9
(b) 66 – _____ =9
(c) 877 – _____ = 99
(d) 666 – _____ = 99
Solution:
This is reverse subtraction
We are given the starting number and the difference and find the number that was subtracted.
We just do:
Starting number – difference = Missing number
(a) 32 – _____ = 9
_____ = 32 – 9
= 23
(6) 56 – _____ = 9
_____ = 56 – 9
= 47
(c) 877 – _____ = 99
_____ = 877 – 99
= 778
(d) 666 – _____ = 99
_____ = 666 – 99
= 567
NCERT Textbook Page 53
Let Us Think and Solve