Cách tìm phân số của một số – Toán lớp 4

Cách tìm phân số của một số như sau: Muốn tìm phân số của một số ta lấy số đó nhân với phân số.

Để tìm được phân số của một số các em cần biết cách nhân phân số. Và xem ví dụ dưới đây:

Ví dụ: Tìm $\displaystyle \frac{2}{5}$

<img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;">

của 145.

Hướng dẫn:

Muốn tìm $\displaystyle \frac{2}{5}$

<img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;">

của 145 ta lấy 145 nhân với $\displaystyle \frac{2}{5}$

<img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;">

.

Vậy $\displaystyle \frac{2}{5}$

<img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;">

của 145 là: $\displaystyle 145\times \frac{2}{5}=58$

<img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-f32f02e67f8f765ef22df8f6282470e3_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle 145\times \frac{2}{5}=58" title="Rendered by QuickLaTeX.com" height="36" width="102" style="vertical-align: -12px;">

Bài tập vận dụng: Một vườn cây có 145 cây ăn quả, trong đó có $\displaystyle \frac{2}{5}$

<img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="data:image/gif;base64,R0lGODlhAQABAAAAACH5BAEKAAEALAAAAAABAAEAAAICTAEAOw==" data-src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="pb-seo-lazy ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;"><noscript><img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-80ea2c441382a4bac0c93cb1b5ad3010_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle \frac{2}{5}" title="Rendered by QuickLaTeX.com" height="36" width="9" style="vertical-align: -12px;">

số cây là cây táo. Hỏi trong vườn có bao nhiêu cây táo.

Cách tìm phân số của một số - Toán lớp 4

Giải:

Số cây táo trong vườn là:

$\displaystyle 145\times \frac{2}{5}=58$

<img decoding="async" src="http://abcdonline.vn/wp-content/ql-cache/quicklatex.com-f32f02e67f8f765ef22df8f6282470e3_l3.png" class="ql-img-inline-formula quicklatex-auto-format" alt="\displaystyle 145\times \frac{2}{5}=58" title="Rendered by QuickLaTeX.com" height="36" width="102" style="vertical-align: -12px;">

(cây táo)

Đáp số : 58 cây táo

Toán lớp 4 - Tags: phân số, toán 4