Trong dãy số sau đây: <span class="MathJax_Preview" style="color: inherit;"><span class="MJXp-math" id="MJXp-Span-1"><span class="MJXp-mstyle" id="MJXp-Span-2"><span class="MJXp-mrow" id="MJXp-Span-3"><span class="MJXp-mn" id="MJXp-Span-4">2</span><span class="MJXp-mo" id="MJXp-Span-5" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-6">0</span><span class="MJXp-mo" id="MJXp-Span-7" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-8">0</span><span class="MJXp-mo" id="MJXp-Span-9" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-10">7</span><span class="MJXp-mo" id="MJXp-Span-11" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-12">2</span><span class="MJXp-mo" id="MJXp-Span-13" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-14">0</span><span class="MJXp-mo" id="MJXp-Span-15" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-16">0</span><span class="MJXp-mo" id="MJXp-Span-17" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-18">7</span><span class="MJXp-mo" id="MJXp-Span-19" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-20">2</span><span class="MJXp-mo" id="MJXp-Span-21" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-22">0</span><span class="MJXp-mo" id="MJXp-Span-23" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-24">0</span><span class="MJXp-mo" id="MJXp-Span-25" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mn" id="MJXp-Span-26">7</span><span class="MJXp-mo" id="MJXp-Span-27" style="margin-left: 0em; margin-right: 0.222em;">,</span><span class="MJXp-mo" id="MJXp-Span-28" style="margin-left: 0em; margin-right: 0.222em;">.</span><span class="MJXp-mo" id="MJXp-Span-29" style="margin-left: 0em; 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padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-11" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">0</span></span><span id="MJXc-Node-12" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-13" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">7</span></span><span id="MJXc-Node-14" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-15" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">2</span></span><span id="MJXc-Node-16" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-17" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">0</span></span><span id="MJXc-Node-18" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-19" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">0</span></span><span id="MJXc-Node-20" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-21" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">7</span></span><span id="MJXc-Node-22" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-23" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">2</span></span><span id="MJXc-Node-24" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-25" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">0</span></span><span id="MJXc-Node-26" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-27" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">0</span></span><span id="MJXc-Node-28" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-29" class="mjx-mn MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="padding-top: 0.396em; padding-bottom: 0.347em;">7</span></span><span id="MJXc-Node-30" class="mjx-mo"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.544em;">,</span></span><span id="MJXc-Node-31" class="mjx-mo MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.347em;">.</span></span><span id="MJXc-Node-32" class="mjx-mo MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.347em;">.</span></span><span id="MJXc-Node-33" class="mjx-mo MJXc-space1"><span class="mjx-char MJXc-TeX-main-R" style="margin-top: -0.145em; padding-bottom: 0.347em;">.</span></span></span></span></span></span></span></span></span><script type="math/tex" id="MathJax-Element-1">\Large {2,0,0,7,2,0,0,7,2,0,0,7,...}</script> a) Số t

Trong dãy số sau đây: 2,0,0,7,2,0,0,7,2,0,0,7,...2,0,0,7,2,0,0,7,2,0,0,7,... a) Số t

4.8/5

Tác giả: Thầy Tùng

Đăng ngày: 18 Aug 2022

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Câu hỏi:

Trong dãy số sau đây: 2,0,0,7,2,0,0,7,2,0,0,7,...2,0,0,7,2,0,0,7,2,0,0,7,...

a) Số thứ 22 là số: ...

b) Tổng của 32 số đầu là: ...

Đáp án án đúng là: B

Lời giải chi tiết:

Ta chia dãy số thành các cặp gồm 4 số ( 2, 0, 0, 7).

a) 22=4×5+222=4×5+2

Vậy số thứ 22 sẽ nằm trong cặp số thứ 6 và là số 0 đầu tiên.

b) Giá trị của một cặp gồm 4 số là: 2 + 0 + 0 + 7 = 9.

32=4×832=4×8

Vậy tổng của 32 số đầu là tổng của 8 cặp 4 số.

Vậy tổng đó là: 9+9+9+9+9+9+9+9=729+9+9+9+9+9+9+9=72