We are asked to select all the true statements from the following: 1. $4 \times 10^{-7}$ is 0.2 times as much as $2 \times 10^{-5}$.

ArithmeticScientific NotationComparisonExponents
2025/4/28

1. Problem Description

We are asked to select all the true statements from the following:

1. $4 \times 10^{-7}$ is 0.2 times as much as $2 \times 10^{-5}$.

2. $2 \times 10^5$ is 40 times as much as $5 \times 10^4$.

3. $6 \times 10^4$ is 2 times as much as $3 \times 10^4$.

4. $7 \times 10^{-5}$ is 0.1 times as much as $7 \times 10^{-3}$.

2. Solution Steps

Statement 1: 4×1074 \times 10^{-7} is 0.2 times as much as 2×1052 \times 10^{-5}.
We need to check if 4×107=0.2×(2×105)4 \times 10^{-7} = 0.2 \times (2 \times 10^{-5}).
0.2×(2×105)=0.4×105=4×101×105=4×1060.2 \times (2 \times 10^{-5}) = 0.4 \times 10^{-5} = 4 \times 10^{-1} \times 10^{-5} = 4 \times 10^{-6}.
Since 4×1074×1064 \times 10^{-7} \neq 4 \times 10^{-6}, this statement is false.
Statement 2: 2×1052 \times 10^5 is 40 times as much as 5×1045 \times 10^4.
We need to check if 2×105=40×(5×104)2 \times 10^5 = 40 \times (5 \times 10^4).
40×(5×104)=200×104=2×102×104=2×10640 \times (5 \times 10^4) = 200 \times 10^4 = 2 \times 10^2 \times 10^4 = 2 \times 10^6.
Since 2×1052×1062 \times 10^5 \neq 2 \times 10^6, this statement is false.
Statement 3: 6×1046 \times 10^4 is 2 times as much as 3×1043 \times 10^4.
We need to check if 6×104=2×(3×104)6 \times 10^4 = 2 \times (3 \times 10^4).
2×(3×104)=6×1042 \times (3 \times 10^4) = 6 \times 10^4.
Since 6×104=6×1046 \times 10^4 = 6 \times 10^4, this statement is true.
Statement 4: 7×1057 \times 10^{-5} is 0.1 times as much as 7×1037 \times 10^{-3}.
We need to check if 7×105=0.1×(7×103)7 \times 10^{-5} = 0.1 \times (7 \times 10^{-3}).
0.1×(7×103)=0.7×103=7×101×103=7×1040.1 \times (7 \times 10^{-3}) = 0.7 \times 10^{-3} = 7 \times 10^{-1} \times 10^{-3} = 7 \times 10^{-4}.
Since 7×1057×1047 \times 10^{-5} \neq 7 \times 10^{-4}, this statement is false.
However, we need to reread the question, since all the check marks are selected, maybe the image is misleading.
Statement 1: 4×1074 \times 10^{-7} is 0.2 times as much as 2×1052 \times 10^{-5}.
0.2×(2×105)=0.4×105=4×101×105=4×1060.2 \times (2 \times 10^{-5}) = 0.4 \times 10^{-5} = 4 \times 10^{-1} \times 10^{-5} = 4 \times 10^{-6}.
Then 4×1074 \times 10^{-7} is 0.1 times as much as 4×1064 \times 10^{-6}
Statement says it's 0.2 times as much as 2×1052 \times 10^{-5}, so false.
Statement 2: 2×1052 \times 10^5 is 40 times as much as 5×1045 \times 10^4.
40×(5×104)=200×104=2×102×104=2×10640 \times (5 \times 10^4) = 200 \times 10^4 = 2 \times 10^2 \times 10^4 = 2 \times 10^6.
Statement says 2×1052 \times 10^5 is 40 times as much as 5×1045 \times 10^4 so false.
Statement 3: 6×1046 \times 10^4 is 2 times as much as 3×1043 \times 10^4.
2×(3×104)=6×1042 \times (3 \times 10^4) = 6 \times 10^4. Statement says 6×1046 \times 10^4 is 2 times as much as 3×1043 \times 10^4 so true.
Statement 4: 7×1057 \times 10^{-5} is 0.1 times as much as 7×1037 \times 10^{-3}.
0.1×(7×103)=0.7×103=7×101×103=7×1040.1 \times (7 \times 10^{-3}) = 0.7 \times 10^{-3} = 7 \times 10^{-1} \times 10^{-3} = 7 \times 10^{-4}.
Statement says 7×1057 \times 10^{-5} is 0.1 times as much as 7×1037 \times 10^{-3}, so false.
After rereading it, statement 2 is true. 2×1052 \times 10^5 is 4 times 5×1045 \times 10^4. No, that's wrong.
2×105=2000002 \times 10^5 = 200000
5×104=500005 \times 10^4 = 50000
200000/50000=4200000 / 50000 = 4
So statement 2 says that 2×1052 \times 10^5 is 40 times as much as 5×1045 \times 10^4. This is wrong, it should be 4 times. So it's false.

3. Final Answer

6×1046 \times 10^4 is 2 times as much as 3×1043 \times 10^4.

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