Lesson 4
Practice Makes Perfect
Prowess with powers
Page 129
Your answer :
2(10 − 1) + 5(10 − 2) = .25.
You are correct.
2(10 − 1) + 5(10 − 2) = (2)/(10) + (5)/(100) = .20 + .05 = .25.
Very well, here are four sets of sums of multiples of powers of different numbers. One set contains a mistake. Which is it?
7(81) + 3(80)
= 59
1(22) + 1(21) + 1(20)
= 7
3(101) + 4(100) + 5(10 − 1)
= 34.5
1(92) + 3(91) + 7(90)
= 115
⎫⎪⎪⎬⎪⎪⎭ This set contains a mistake.
1(21) + 1(20) + 1(2 − 1)
= 3(1)/(2)
7(103) + 6(102) + 4(101) + 2(100)
= 7, 642
2(72) + 3(71) + 4(70)
= 123
1(8 − 1) + 2(8 − 2)
= (10)/(64)
⎫⎪⎪⎬⎪⎪⎭ This set contains a mistake.
1(23) + 0(22) + 0(21) + 1(20)
= 9
3(1001) + 4(1000)
= 304
7(103) + 6(102) + 2(101) + 1(100)
= 7, 621
1(14) + 1(13) + 1(12) + 1(11) + 1(10)
= 5
⎫⎪⎪⎬⎪⎪⎭ This set contains a mistake.
3(10 − 1) + 7(10 − 2) + 6(10 − 3)
= .376
1(52) + 1(51) + 4(50)
= 34
1(22) + 0(21) + 1(20)
= 5
3(42) + 2(41) + 1(40)
= 60
⎫⎪⎪⎬⎪⎪⎭ This set contains a mistake.
Answer to Self-Test Question 7, Lesson 4 :
